SP Power Systems Ltd - Part 2 - Standards

Appendix 5 to the Proof of Evidence

Of

Eric Paalman

On

Engineering Project Design

SPM/ENGINEERING/POE/PAALMAN/003C

Enter Enquiry No Enquiry No. PART 2 Page 1

SP Power Systems Ltd 2005 Part 2 Standards - Generic Document.doc

SP Power Systems Ltd

ENQUIRY No.

SP Power Systems Ltd - Part 2 - Standards

CONTENTS

INTRODUCTION ..................................................................................................................................... 6

SP POWER SYSTEMS LTD TRANSMISSION AND DISTRIBUTION SYSTEM .................................. 8 System Voltages ................................................................................................................................. 8 System Voltages ................................................................................................................................. 8 System Frequency .............................................................................................................................. 9 Short Circuit and Continuous Current Magnitudes ............................................................................. 9 Maximum Fault Current Infeed And X/R Ratio Values ..................................................................... 10

PRIMARY CIRCUIT CAPACITANCE CURRENTS ............................................................................. 11 Transformer Magnetising Inrush Currents ........................................................................................ 11 Maximum Oscillatory Currents .......................................................................................................... 12 Earthing Of System Neutral .............................................................................................................. 12 Waveform Quality ............................................................................................................................. 12 Substation Electrical Clearances ...................................................................................................... 13 Substation Safety Clearances .......................................................................................................... 13 Clearances To Roadways ................................................................................................................. 13 Maximum Equipment Heights In Substations ................................................................................... 14

1 SUBSTATIONS ............................................................................................................................ 15 1.1 Scope ................................................................................................................................... 15 1.2 References........................................................................................................................... 15 1.3 General Substation Requirements ...................................................................................... 17

2 MAIN PLANT ............................................................................................................................... 21 2.1 Scope ................................................................................................................................... 21 2.2 References........................................................................................................................... 21 2.3 Switchgear Rated at 145kV, 300kV and 420KV .................................................................. 24 2.4 33kV Shunt Reactor Circuit Breakers .................................................................................. 26 2.5 36kV Rated Switchgear ....................................................................................................... 26 2.6 25kV AC Single phase switchgear and ancillary equipment ............................................... 26 2.7 12kV Rated Switchgear ....................................................................................................... 26

3 TRANSFORMERS AND REACTORS ......................................................................................... 27 3.1 General ................................................................................................................................ 27 3.2 Double-Wound and Auto Transformers ............................................................................... 29 3.3 Earthing / Auxiliary Transformers ........................................................................................ 40

4 OVERHEAD LINES...................................................................................................................... 44 4.1 sPECIFICATIONS AND STANDARDS ............................................................................... 44 4.2 GENERAL ............................................................................................................................ 46 4.3 CONDUCTORS ................................................................................................................... 49 4.4 VIBRATION DAMPERS ....................................................................................................... 55 4.5 JOINTS AND CLAMPS ........................................................................................................ 55 4.6 BI-METAL CONNECTORS .................................................................................................. 58 4.7 SPACERS FOR BUNDLE CONDUCTORS ........................................................................ 58 4.8 INSULATORS AND FITTINGS ............................................................................................ 59 4.9 STEEL TOWERS ................................................................................................................. 61



4.10 FOUNDATIONS ................................................................................................................... 65 4.11 CODE OF BEHAVIOUR ...................................................................................................... 70 4.12 SPECIMEN FORMS ............................................................................................................ 73 4.13 WIRING CHECKING RECORDS ........................................................................................ 74 4.14 TOWER FOUNDATION CHECKING RECORD .................................................................. 76 4.15 TOWER ERECTION / CHECKING RECORDS ................................................................... 78

5 TRANSMISSION CABLES .......................................................................................................... 80 5.1 References........................................................................................................................... 80 5.2 CABLE SYSTEM ................................................................................................................. 83 5.3 Conductor Thrust ................................................................................................................. 84 5.4 Fluid Filled Cable System .................................................................................................... 84 5.5 POLYMERIC CABLE SYSTEM ........................................................................................... 85 5.6 RAILWAY REGULATIONS .................................................................................................. 85 5.7 SERVING OF NOTICES ...................................................................................................... 85 5.8 CIVIL WORKS EXCAVATION AND REINSTATEMENT OF TRENCHES ....................... 86 5.9 UNDERGROUND OPTICAL FIBRE CABLES ..................................................................... 86

6 PROTECTION .............................................................................................................................. 88 6.1 REFERENCES .................................................................................................................... 88 6.2 GENERAL REQUIreMENTS ............................................................................................... 89 6.3 PROTECTION FUNCTIONAL REQUIREMENTS ............................................................... 92 6.4 REMOTE INDICATION AND ALARM FACILITIES ............................................................. 97 6.5 OPERATOR INTERFACES ................................................................................................. 97 6.6 ENVIRONMENTAL REQUIREMENTS ................................................................................ 99 6.7 EQUIPMENT LIFE AND LIFETIME SUPPORT .................................................................. 99 6.8 TYPE ASSESSMENT ........................................................................................................ 100

7 CONTROL .................................................................................................................................. 101 7.1 REFERENCES .................................................................................................................. 101 7.2 GENERAL .......................................................................................................................... 101 7.3 Substation Control & Information Systems ........................................................................ 101 7.4 Controls, Indication and Alarm Facilities ........................................................................... 101 7.5 Standby Control Boards ..................................................................................................... 104 7.6 Telemetering ...................................................................................................................... 104 7.7 Sychronising and Voltage Selection .................................................................................. 104 7.8 Automatic Voltage Control ................................................................................................. 104

8 TELECOMMUNICATIONS ........................................................................................................ 105

9 METERING AND INSTRUMENTATION .................................................................................... 106 9.1 REFERENCES .................................................................................................................. 106 9.2 GENERAL REQUIREMENTS ............................................................................................ 106 9.3 Substation Clock ................................................................................................................ 106 9.4 Electrical Measurement Transducers ................................................................................ 106

10 CIVIL & BUILDING .................................................................................................................... 107 10.1 Civil Design Standards ...................................................................................................... 107 10.2 Design Methodology .......................................................................................................... 108 10.3 Civil Design Calculations, Details and Drawings ............................................................... 108 10.4 Site Studies ........................................................................................................................ 109 10.5 Materials and Workmanship .............................................................................................. 109 10.6 Setting Out ......................................................................................................................... 110 10.7 Services ............................................................................................................................. 110 10.8 Method Statements and Risk Assessments ...................................................................... 111 10.9 Site Clearance and Excavation.......................................................................................... 111 10.10 Earthworks and Platform Construction .......................................................................... 112 10.11 Substation Roads .......................................................................................................... 113 10.12 Height Gauges and Bollards ......................................................................................... 113 10.13 Disposal of Water .......................................................................................................... 114 10.14 New Palisade Security Fencing..................................................................................... 114



10.15 Concrete Works ............................................................................................................. 114 10.16 Transformer/Reactor Foundation Complex ................................................................... 115 10.17 Cable Trenches ............................................................................................................. 115 10.18 Aluminium and Steel Support Structures ...................................................................... 116 10.19 Cable Route Excavations .............................................................................................. 117 10.20 DRAINAGE .................................................................................................................... 117 10.21 External Perimeter Footpath ......................................................................................... 118 10.22 Site Reinstatement ........................................................................................................ 118 10.23 Building Work ................................................................................................................ 119 10.24 Site Reinstatement ........................................................................................................ 126 10.25 Pre-cast Concrete Repairs ............................................................................................ 126 10.26 Demolition/Dismantling of Concrete Structures and Buildings. ..................................... 126 10.27 Cables Outwith Trenches .............................................................................................. 126 10.28 Miscellaneous Works .................................................................................................... 127

11 NOT USED ................................................................................................................................. 127

12 SUBSTATION AUXILIARY SUPPLIES ..................................................................................... 128 12.1 Scope ................................................................................................................................. 128 12.2 References......................................................................................................................... 128 12.3 LVAC Equipment ............................................................................................................... 130

13 AUTOMATIC SWITCHING ........................................................................................................ 133 13.1 REFERENCES .................................................................................................................. 133 13.2 GENERAL REQUIREMENTS ............................................................................................ 133 13.3 Delayed Automatic Reclosure and Plant Isolation............................................................. 133 13.4 Ferroresonance Switching ................................................................................................. 133

14 LANDSCAPING AND PLANTING ............................................................................................. 134 14.1 Personal Protective Equipment ......................................................................................... 134 14.2 Herbicides & Pesticides ..................................................................................................... 134 14.3 Herbicide Type ................................................................................................................... 134 14.4 Adjuvant (Wetting Agent) ................................................................................................... 135 14.5 Herbicide Log Book ........................................................................................................... 135 14.6 Notice to Public .................................................................................................................. 135 14.7 Herbicide Equipment ......................................................................................................... 135 14.8 Health and Safety Information ........................................................................................... 135 14.9 Stripping of Topsoil and Subsoil ........................................................................................ 136 14.10 Storage of Topsoil and Subsoil ..................................................................................... 136 14.11 Handling of Topsoil and Subsoil .................................................................................... 136 14.12 Topsoil Application ........................................................................................................ 137 14.13 Topsoil Depths............................................................................................................... 137 14.14 Slopes ............................................................................................................................ 137 14.15 Maintenance of Soiled Areas until Planting ................................................................... 137 14.16 Approvals ....................................................................................................................... 137 14.17 Work by Machine or Hand ............................................................................................. 138 14.18 Application of Herbicide ................................................................................................. 138 14.19 Cultivation of Planted Areas Including Hedgerows ....................................................... 138 14.20 Cultivation of Grassed Areas ......................................................................................... 139 14.21 Grass Areas ................................................................................................................... 139 14.22 Existing Burn & Ditches ................................................................................................. 139 14.23 Treatment Of Dead, Dying & Damaged Vegetation ...................................................... 139 14.24 Safety Clearance Corridors ........................................................................................... 139 14.25 Existing Woodland Areas .............................................................................................. 140 14.26 Installation of fencing ..................................................................................................... 140 14.27 Timber ........................................................................................................................... 140 14.28 Fittings ........................................................................................................................... 140 14.29 Site Cutting Of Timber ................................................................................................... 141 14.30 Damage To Galvanised Surfaces ................................................................................. 141 14.31 Removal of Existing Fencing ......................................................................................... 141 14.32 Soft Landscaping Generally .......................................................................................... 141



14.33 Substitution .................................................................................................................... 142 14.34 Trees and Hedgerows Generally................................................................................... 142 14.35 Bare Rooted Plants ....................................................................................................... 143 14.36 Container Grown / Root-balled Plants ........................................................................... 143 14.37 Tree Tubes and Stakes ................................................................................................. 143 14.38 Fertiliser ......................................................................................................................... 144 14.39 Root Dip ......................................................................................................................... 144 14.40 Inorganic Fertiliser ......................................................................................................... 144 14.41 Hedgerow Mulch............................................................................................................ 144 14.42 Transport and Handling ................................................................................................. 144 14.43 Storage .......................................................................................................................... 145 14.44 Planting [Season] .......................................................................................................... 145 14.45 Planting Conditions ....................................................................................................... 145 14.46 Planting Generally ......................................................................................................... 146 14.47 Planting Pits ................................................................................................................... 146 14.48 Transplants and Shrubs ................................................................................................ 147 14.49 Backfill and Fertiliser ..................................................................................................... 147 14.50 Hedgerow Planting ........................................................................................................ 148 14.51 Hedgerow Mulch............................................................................................................ 148 14.52 Pruning .......................................................................................................................... 148 14.53 Tree Stakes ................................................................................................................... 148 14.54 Watering ........................................................................................................................ 148 14.55 Grass Seeding ............................................................................................................... 148 14.56 Grass Seed Mixes: ........................................................................................................ 149 14.57 Water ............................................................................................................................. 149 14.58 Germination ................................................................................................................... 150 14.59 First Cut ......................................................................................................................... 150 14.60 General Maintenance of Planted Areas prior to practical completion .......................... 150 14.61 Defects Liability Period .................................................................................................. 150 14.62 Generally ....................................................................................................................... 151 14.63 Visits .............................................................................................................................. 151 14.64 Operating Conditions ..................................................................................................... 151 14.65 Maintenance .................................................................................................................. 152 14.66 Watering ........................................................................................................................ 152 14.67 Drought Conditions ........................................................................................................ 152 14.68 Removal of Rubbish ...................................................................................................... 153 14.69 Checking of Staking ...................................................................................................... 153 14.70 Pruning .......................................................................................................................... 153 14.71 Weed Control................................................................................................................. 153 14.72 Pest/Disease Control ..................................................................................................... 154 14.73 Refirming Plants ............................................................................................................ 154 14.74 Cutting Meadow Areas .................................................................................................. 154 14.75 Hedgerows .................................................................................................................... 154 14.76 Maintenance of Fences and Stiles ................................................................................ 154



Amendment Record

Issue Date Summary of Changes/Reason Author(s) Approved By

(Inc. Job Title)

1 Nov 2009 System Voltages updated to SPTS 1

System frequency updated to SPTS 1

E/F factors updated to SPTS 1

11kV BIL added

Gilbert Mpofu



INTRODUCTION

This part specifies the Employers technical requirements for plant, equipment, apparatus and services for use on its transmission and distribution systems at 400 kV, 275 kV, 132 kV and 33 kV, 25kV and 11kV.

Extensive reference is made to National Grid Company plc engineering documents, especially Technical Specifications (NGTS) and Electricity Association Technical Specifications (EATS) . Copies of National Grid Company plc engineering documents may be obtained from:

National Grid Transco plc NGT House Warwick Technical Park Gallows Hill Warwick CV34 6DA

Copies of Electricity Association Technical Specifications may be obtained from:

The Electricity Association 30 Millbank London

SW1P 4RD

The Approval status within SP Power Systems of external documents is agreed by the Employers Technical Documentation Approvals Panel (TDAP). Employers documents detailing the Approval status are subject to review whenever a new issue of the subject document is published or, if none, no later than three years from issue date.

In all NGC engineering documents, for "NGC" read "SP Power Systems Ltd".

Where this part amends a National Grid Company plc engineering document, references made to that document in other NGC engineering documents shall be taken to include those amendments.

In the case of the sections covering Protection, Control, Metering and Instrumentation, and Automatic Switching sections of Part 2, extensive reference is made to the Employers standards.

References to the Employers standards and documents shall be understood to be references to the edition applicable 28 days prior to the latest date for submission of the tender, unless otherwise stated.

Copies of the Employers standards and documents may be obtained from:

Documentation Section SP Power Systems Ltd New Alderston House



Strathclyde Business Park Dove Wynd Bellshill

Lanarkshire ML4 3FF



SP POWER SYSTEMS LTD TRANSMISSION AND DISTRIBUTION SYSTEM

The SP Power Systems Ltd Transmission and Distribution System operating at a nominal voltage of 400 kV and below, is defined in terms of conditions and ratings to which plant and equipment connected to it may be subjected in the following schedules.

All Plant and equipment supplied shall comply with the Health and Safety at Work Act 1974, The Factories Act 1961, The Electricity at Work Regulation 1989 and other relevant legislation.

Plant and equipment connected to the SP Power Systems Ltd Transmission and Distribution System must operate satisfactorily and safely under the conditions specified. The following schedules provide detailed information on:

System Voltages System Frequency Short Circuit and Continuous Current Magnitudes Maximum Fault Current In feed and Circuit X/R Ratios Primary Circuit Capacitance Currents Transformer Magnetising Inrush Currents Maximum Oscillatory Currents Earthing of System Neutral Points Waveform Quality Substation Electrical Clearances Substation Safety Clearances Clearance to Roadways Maximum Equipment heights in Substations

SYSTEM VOLTAGES

SYSTEM VOLTAGES Nominal System Voltage 400 kV 275 kV 132 kV 33 kV 11kV Maximum System Voltage (i) 420 kV (ii) 303 kV 145 kV 34.98 kV 11.66 kV Minimum System Voltage (i) 360 kV 247 kV 119 kV 31.02 kV 10.34 kV Rated Voltage of Primary Equipment (iii)

420 kV 300 kV 145 kV 36 kV 12 kV

i). These limits may be exceeded in abnormal conditions. ii). Maximum voltage may be 440 kV for a maximum of 15 minutes. iii). Except where otherwise specified.



SYSTEM FREQUENCY

Plant and Equipment shall satisfy their specified functional and performance requirements over the range of frequencies given in the table below.

Plant and Equipment shall also operate safely and without any degradation in performance within the following frequency ranges:

i). 47Hz to 47.5 Hz for at least 20 seconds ii). 50.5 to 52 Hz continuous

SHORT CIRCUIT AND CONTINUOUS CURRENT MAGNITUDES

The following table represents the anticipated maximum system conditions.

The short circuit currents listed may be subject to 100% asymmetry. Short circuit and continuous current magnitudes: System Voltage 400 kV 275 kV 132 kV 33 kV 11 kV

Maximum 3 phase symmetrical short circuit current/kA 50 for

1 sec

31.5 for

1 sec

20 for

3 secs

17.5 for

3 secs

13.1 for

3 secs

Maximum single phase short circuit current/kA

55 for 1 sec

40 for 1 sec

25 for 3 secs

4.2 for 3 secs

*

13.1 for 3 secs

Minimum symmetrical short circuit current/kA

0.4 0.5 0.5 N/a N/a

Maximum Continuous Circuit Currents/kA (Balanced)

Overhead Lines

4.7 2.8 2.5 0.8 0.8

Cable 4.0 2.5 2.5 0.8 0.7

* In the case of 33kV cables connecting the lower voltage side of a power transformer to the 33kV network, the maximum single phase duration is 8 seconds

Rated Frequency 50 Hz

Maximum continuous frequency 50.5 Hz

Minimum continuous frequency 49.5 Hz



MAXIMUM FAULT CURRENT INFEED AND X/R RATIO VALUES

The data given in this table is derived from system conditions in which a minimum circuit (overhead line) length of 10 km is assumed. Where lines of less than 10 km are considered, the contract specifications will identify the requirement.

It should be noted that the maximum values of IF and X/R do not necessarily occur co-incidentally with the result that (IF(X/R)) max is not necessarily equal to the product of (IF) max and (X/R) max.

(IF) max in kA

(X/R) max

(IF(X/R)) max

Generator Fed Fault

Internal 7.2 88 630

400kV External 6.3 69 370

System Fed Fault

Internal 55 31 1200

External 31 28 620

Generator Fed Fault

Internal 10.4 88 910

275kV External 8.0 57 420

System Fed Fault

Internal 40 32 800

External 20 50 400

Generator Fed Fault

Internal 5 50 250

132kV External 10 20 200

System Fed Fault

Internal 25 20 500

External 15 20 300



PRIMARY CIRCUIT CAPACITANCE CURRENTS

System Voltage (kV)

Type of Circuit

Range of Capacitance

Current (A/km)

Maximum Circuit

Length (km) Maximum

Capacitance Current (A)

400 Overhead Line 0.8 - 1.0 128 128

Cable 20.0 - 56.0 2.5 140 Composite - 128/2.5 268

275 Overhead Line 0.5 - 0.7 80 56

Cable 16.0 - 24.0 5.5 132 Composite

(OHL/Cable) - 76/0.5 65

132 Overhead Line 0.22 - 0.32 68 22

Cable 7.0 - 18.6 6.3 113 Composite

(OHL/Cable) - 69/1.8 55

This table gives the maximum values of 50 Hz capacitance current for two-ended 400, 275 and 132 kV overhead line, underground cable and composite overhead line/underground cable circuits under balanced rated voltage conditions. For circuits of predominantly underground cable construction, reactive compensation plant may be provided to reduce the capacitance current values given in this table. The amount of reactive compensation employed in such cases will not normally exceed 60% of the maximum cable capacitance current, and will normally be connected at one end either inside the protected zone of the circuit close to the circuit breakers or just outside the protected zone of the circuit.

TRANSFORMER MAGNETISING INRUSH CURRENTS

System Voltage

HV/LV (kV) Range of

Transformer Ratings (MVA)

Peak Inrush Current.

(Energised form HV Side)

Peak Inrush Current.

(Energised form LV

Side)

Range of Transforme

r X/R

400/275,132 240 - 1000 1.7 - 8.0 pu 2.1 - 8.1 pu 50 - 140 275/132 75 - 240 4.75 - 14.5 pu Not

Applicable 40 - 100



MAXIMUM OSCILLATORY CURRENTS

Incident Pk-Pk Envelope Current (A rms)

Repetition Rate of Oscillatory Envelope (Hz)

Maximum Duration (s)

Power Swing 1,800 0.5 - 1.5 10 Pole-Slip 10,000 0.5 5 10

Steady State System Oscillation

1,200 0.5 - 1.0 300

EARTHING OF SYSTEM NEUTRAL

Nominal Voltage/kV Max E/F Factor Earthing Type 400 1.4 Multiple Direct 275 1.4 Multiple Direct 132 1.4 Multiple Direct 33 1.9 Multiple Resistance 11 1.6 Multiple Direct

WAVEFORM QUALITY

Harmonic Number Harmonic Current 2nd 40 A

3rd 70 A

4th 25 A

5th 30 A

7th 35 A

9th 10 A

11th 15 A

The harmonic current levels give in the table can occur simultaneously. Other harmonics may be assumed to be negligible.



SUBSTATION ELECTRICAL CLEARANCES

Nominal System Voltage/kV (rms)

BIL,SIL/kVp Basic Electrical Clearance (phase to earth)/m

Phase to Phase Clearance/m

11 75 0.2 0.25 33 170 0.5** 0.5** 132 650* 1.2 1.4 275 1050/850 2.1 2.4 400 1425/1050 3.0 3.6

* Where the specification covers the supply of a transformer this figure should be substituted by 550kV.

** Note that these figures can be relaxed to 0.38 phase/earth and 0.43 phase/phase for type tested equipment as per BS162.

SUBSTATION SAFETY CLEARANCES

Nominal System Voltage/kV

Safety Distance (from SP Safety

Rules)/m Design

Clearance for Safety/m

Insulation Height (pedestrian access)/m

33 & 11 0.8 3.2 2.4 132 1.4 3.8 2.4

275 2.4 4.8 2.4

400 3.1 5.5 2.4

CLEARANCES TO ROADWAYS Nominal System Voltage/kV Minimum Clearance to Roadways/m

33 & 11 5.6

132 6.2

275 7.2

400 7.9



MAXIMUM EQUIPMENT HEIGHTS IN SUBSTATIONS Nominal System Voltage/kV Maximum Equipment Height/m

132 10

275 13

400 16



1 SUBSTATIONS

1.1 SCOPE

This section of the specification describes the substation technical requirements.

This section applies to all of the transmission and distribution networks owned by the Employer at 400kV, 275kV, 132kV, 33kV, 25kV and 11kV.

1.2 REFERENCES

This part of the specification makes extensive reference to National Grid Company plc engineering documents: Technical Specifications (NGTS), Transmission Plant Specifications (TPS) and Transmission Design Memorandums (TDM). The contents of National Grid Company plc engineering documents are based on the needs of NGC and the conditions under which it operates and do not necessary meet the circumstances and requirements of the Employer. Where the Employers requirements differ from the provisions of NGTS and TDM documents the TDAP shall issue a document accepting the subject document with modifications. The TDAP document reference shall include the number 12 to indicate this.

Where the Employers requirements are similar to the provisions of NGTS and TDM documents the TDAP shall issue a document accepting the subject document without modifications. The TDAP document reference shall include the number 11 to indicate this. Where the Employers requirements differ from the provisions of NGC TPS documents, the Employer has modified and re-issued the TPS under a 10,000 series number. In addition, the Employer issues internally generated TPS documents in the 10,000 series.

In the case of 132kV where TPS does not apply, reference to other ESI standards has been made in the text.

In the case of 33 kV, reference to related SP Power Systems Ltd standards and EATS standards has been made in the text.

This specification refers to and shall comply with the following documents. In all documents, for NGC read SP Power Systems Ltd. Where a document refers to another NGTS document, the reference shall be taken to include the amendments in the relevant part of this Section.

Subject to the approval of the Employers Representative, the tenderers may adopt standards or codes of practice issued by the European union provided that such standards or codes of practice can be demonstrated to be of an equivalent or higher standard than the relevant British Standards or Codes of Practice. The tenderer shall supply the Employers Representative with single copies of each alternative standard or code proposed.



1.2.1 NATIONAL GRID TECHNICAL SPECIFICATIONS

NGTS 1, as modified by SP Power Systems document NG-12-040 Apparatus and Services for the National Grid System and Direct Connections to it.

NGTS 2.1, as modified by SP Power Systems document NG-12-041 Substations

NGTS 2.10, as accepted by SP Power Systems document NG-11-002 Civil Engineering and Building Works

NGTS 2.13, as accepted by SP Power Systems document NG-11-049 Electronic Equipment

NGTS 2.19, as modified by SP Power Systems document NG-12-035 Ancillary Light Current Equipment

NGTS 3.1.1, as modified by SP Power Systems document NG-12-036 Interlocking

NGTS 3.1.2, as modified by SP Power Systems document NG-12-037 Substation Earthing (reference is made in specification to BS CECC 0015 for earth studs)

1.2.2 TRANSMISSION PLANT SPECIFICATIONS

TPS 10/11 Limitation of Fire risk in Substations, Switchhouses, Cable Basements, Transmission Cable Tunnels and Cable Bridges

TPS 13/10001 Standardisation of Circuit Nomenclature

1.2.3 ELECTRICITY ASSOCIATION TECHNICAL SPECIFICATIONS

09-06 Auxiliary Multicore and Multipair Cables

12-24 Plastic ducts for buried electric cables.

41-21 Portable earthing Equipment for Open Type HV Apparatus in Substations

41-24 Guidelines for the Design, Installation, Testing and Maintenance of Main Earthing Systems in Substations

48-5 Environmental Test Requirements for Protection & Relays



1.3 GENERAL SUBSTATION REQUIREMENTS

The substation technical requirements shall comply with NGTS 1, as modified by SP Power Systems document NG-12-040 and NGTS 2.1, as modified by SP Power Systems document NG-12-041.

As part of the requirements of this specification, it is the responsibility of the successful tenderer to design and produce all electrical layouts. If they are included with this specification they are issued on a notional basis for tendering purposes only.

1.3.1 Interlocking

The interlocking scheme shall comply with NGTS 3.1.1, as modified by SP Power Systems document NG-12-036. Where motorised line earth switches are specified, the interlocking scheme shall comply with the Employers Technical Guidance Note and shall not invalidate the disconnector or earth switch manufactures guarantee. The scheme and installation shall be to the satisfaction of the Employers Representative

The successful tenderer shall provide full details of the materials proposed to prevent corrosion for outdoor interlocking barrels, keys and associated fittings that are not normally located in a protective housing. The corrosion prevention shall be provided to the satisfaction of the Employers Representative.

1.3.2 Substation Earthing

It is the responsibility of the successful tenderer to ascertain the resistivity of the soil at the site. If values are included with this specification, they are for tender purpose only. Any significant differences between the values supplied and the values obtained at the commencement of the site work shall be subject of discussion at that stage.

The earthing system shall be designed, installed and tested in accordance with EATS 41-24 and NGTS 3.1.2, as modified by SP Power Systems document NG-12-037.

The high frequency earthing system shall be designed, installed and tested in accordance with NGTS 3.1.2, as modified by SP Power Systems document NG-12-037.

1.3.3 Enclosures and Small Wiring

This clause specifies the requirements for indoor and outdoor enclosures. It does not cover mechanism boxes or other boxes which form an integral part of primary equipment. All equipment shall be designed for a normal service life of forty years.



Enclosures and small wiring shall be in accordance with NGTS 2.19, as modified by SP Power Systems document NG-12-035.

In accordance with NGTS 3.1.2, as modified by SP Power Systems document NG-12-037, means shall be provided for connecting each enclosure to the substation earthing system. The design shall meet safety and EMC requirements. Where enclosures contain electronic equipment, they shall be supplied with an earth stud in compliance with BS CECC 0015. Where the enclosure earth and location earth are different the enclosure must be suitably insulated to reduce the risk from transfer potentials

Tenderers in their offer shall state their proposals to prevent corrosion of outdoor enclosures. Consideration shall be given to heating, ventilation and drainage.

For indoor and outdoor enclosures anti-vermen protection shall be provided and the method of protection shall be to the approval of the Employers Representative.

Tenderers shall include with their offer details of crimps, crimping systems, wires, terminals and terminations they propose to use.

In existing substations wire numbering is in accordance with BEBS S-12. For substation modifications the new wiring shall also be in accordance with this standard. For new substations the Tenderer shall state the numbering system he proposes to use.

In accordance with NGTS 3.12.3, as modified by SP Power Systems document NG-12-002, outdoor marshalling kiosks (bay and transformer) shall be provided with 110, 230 and 400V LVAC supplies and sockets.

1.3.4 Multicore and Low Voltage Cables

Multicore cables for protection, control and small power shall be in accordance with EATS 09-6 and BS6724, respectively.

In joint-user substations to which third party staff routinely has access, it is the Employers preference to use low smoke multi-core and multi-pair cabling. Where the tenderer considers it unnecessary to install low smoke cabling, they shall carry out a risk assessment to justify the use of a different type of cable. This risk assessment shall be made available to the Employer on request.

The successful tenderer shall provide complete multicore cable and low voltage cable schedules showing the locations of all new cabling and any existing cabling.

1.3.5 Aluminium and Steel Support Structures

1.3.5.1 Design

The Contractor shall be responsible for the design, manufacture and supply of all structural steelwork and aluminium support structures required for the works. The



structures shall be delivered to site complete with all predrilled holes for the fixing of earth tapes, cables and all other relevant attachments. In addition, where required, they shall be supplied with suitable drain holes. Site drilling after erection shall not be permitted.

Structures shall be used for bonding of electrical equipment to an earth mat and evidence shall be provided which demonstrates that the structure is capable of withstanding the rated short time current. Where practicable, bolted structures shall be avoided.

The design of support structures shall comply also with the requirements of NGTS 2.1, as modified by SP Power Systems document NG-12-041.

Structure designs that have been used in the past are included in the schedule of standard drawings. However, it is stressed that these are for guidance only and should the Tenderer utilise them, they are still responsible for ensuring that the structures comply with their designs and are in full compliance of this specification.

1.3.5.2 Serviceability

When considering the serviceability of the of the supporting structures, the Contractor shall ensure that deflections are appropriate for the proper function of the structure and for the plant and equipment supported by the structure but in any case, shall not be greater than that recommended in the appropriate British Standard.

1.3.5.3 Finishes

The finishes applied to structural steelwork elements shall have a uniform appearance and shall be appropriate for the level of corrosion protection for the required 40 year design life of the substation.

The holes drilled in the structure to accommodate the galvanising process shall be fitted with suitable plugs.

1.3.6 Floodlighting and Security Systems

The floodlighting system shall comply with NGTS 2.1, as modified by SP Power Systems document NG-12-041, and the facility shall be provided to control its operation remotely and manually from the control room and the substation perimeter access gate.

The intruder alarm system shall be designed, installed and tested to the satisfaction of the Employers Representative. Where a floodlighting system has been specified in Part 1 of this Specification, the Tenderer shall, where appropriate, utilise the same structures for the cameras and floodlights to minimise the number of structures in the compound.



The earthing requirements for the floodlighting and intruder alarms systems shall comply with NGTS 3.1.2, as modified by SP Power Systems document NG-12-037.

1.3.7 Electromagnetic Compatibility

The European Commission legislation on Electromagnetic Compatibility became mandatory on 1 January 1996.

In order to ensure compliance with the legislation, it is essential that all electrical equipment offered must meet the legislation requirements and are marked accordingly. Equipment suppliers must state the means by which compliance is achieved and supply the associated conformity documentation.

In addition, the Contractor must ensure that electromagnetic compatibility is achieved within the substation particularly with the increasing application of micro-processor based equipments.

Where secondary equipment is located within the control and relay building or within separate relay rooms or within outdoor enclosures it shall be designed to ensure adequate protection against electromagnetic interference and shall comply with EATS 48-5 & NGTS 2.13.

At the time of commissioning, circuit-breaker and disconnector normal switching operations shall be performed to demonstrate that EMC has in fact been achieved within the substation environment.

In addition, the substation itself will need to achieve EMC compliance against third party interference. Where specified in Part 1 of this specification, the emission levels at the substation perimeters will also need to be assessed and measured during the switching operations described above.



2 MAIN PLANT

2.1 SCOPE

This section of the specification describes the functional and performance requirements for the switchgear and associated equipment.

This section applies to all of the transmission and distribution networks owned by the Employer at 400kV, 275kV, 132kV, 33kV, 25kV and 11kV.

2.2 REFERENCES

This part of the specification makes extensive reference to National Grid Company plc engineering documents: Technical Specifications (NGTS), Transmission Plant Specifications (TPS) and Transmission Design Memorandums (TDM). The contents of National Grid Company plc engineering documents are based on the needs of NGC and the conditions under which it operates and do not necessary meet the circumstances and requirements of SP Power Systems Ltd.

Where SP Power Systems Ltd requirements differ from the provisions of NGTS's and TDM's the TDAP shall issue a document accepting the subject document with modifications. The TDAP document reference shall include the number 12 to indicate this.

Where SP Power Systems Ltd requirements are similar to the provisions of NGTS and TDM documents the TDAP shall issue a document accepting the subject document without modifications. The TDAP document reference shall include the number 11 to indicate this.

Where the Employers requirements differ from the provisions of NGC TPS documents, the Employer has modified and re-issued the TPS under a 10,000 series number. In addition, SP Power Systems Ltd issue internally generated TPS documents in the 10,000 series.

In the case of 132kV where TPS does not apply, reference to other ESI standards has been made in the text.

In the case of 33 kV, reference to related SP Power Systems Ltd standards and EATS standards has been made in the text.

This specification refers to and shall comply with the following documents. In all documents, for NGC read SP Power Systems Ltd. Where a document refers to another NGTS document, the reference shall be taken to include the amendments in the relevant part of this Section.

Subject to the approval of the Employers Representative, the successful tenderer may adopt standards or codes of practice issued by the European union provided that such standards or codes of practice can be demonstrated to be of an equivalent or higher standard than the relevant British Standards or Codes of Practice.



The successful tenderer shall supply the Employers Representative with single copies of each alternative standard or code proposed.

2.2.1 NATIONAL GRID TECHNICAL SPECIFICATIONS

NGTS 1, as modified by SP Power Systems document NG-12-040 Ratings and General Requirements for Plant, Equipment, Apparatus and Services for the National Grid System and Direct Connections to it.

NGTS 2.2, as modified by SP Power Systems document NG-12-043 Switchgear

NGTS 2.10, as accepted by SP Power Systems document NG-11-002 Civil Engineering and Building Works

NGTS 2.13, as accepted by SP Power Systems document NG-11-049 Electronic Equipment

NGTS 2.19, as modified by SP Power Systems document NG-12-035 Ancillary Light Current Equipment

NGTS 3.1.1, as modified by SP Power Systems document NG-12-036 Interlocking

NGTS 3.1.2, as modified by SP Power Systems document NG-12-037 Substation Earthing

NGTS 3.2.1, as modified by SP Power Systems document NG-12-034 Circuit Breakers and Switches

NGTS 3.2.2, as modified by SP Power Systems document NG-12-038 Disconnectors and Earthing Switches

NGTS 3.2.3, as modified by SP Power Systems document NG-12-039 Surge Arresters

NGTS 3.2.4, as modified by SP Power Systems document NG-12-012 Current Transformers

NGTS 3.2.5, as accepted by SP Power Systems document NG-11-044 Voltage Transformers

NGTS 3.2.6, as modified by SP Power Systems document NG-12-013 Current and Voltage Transformers

NGTS 3.2.7, as accepted by SP Power Systems document NG-11-045 Bushings



NGTS 3.2.9, as accepted by SP Power Systems document NG-11-046 Post Insulators

2.2.2 TRANSMISSION PLANT SPECIFICATIONS

TPS 10/11 Limitation of Fire risk in Substations, Switchhouses, Cable Basements, Transmission Cable Tunnels and Cable Bridges

TPS 13/10001 Standardisation of Circuit Nomenclature

2.2.3 ELECTRICITY ASSOCIATION TECHNICAL SPECIFICATIONS

41-21 Portable earthing Equipment for Open Type HV Apparatus in Substations

41-24 Guidelines for the Design, Installation, Testing and Maintenance of Main Earthing Systems in Substations


2.2.4 OTHER STANDARDS

S2 SP Power Systems Ltd specification: 12kV Distribution metalclad indoor switchgear and protection equipment for indoor primary and customer substations.

P.24 Engineering Recommendation: A.C. Traction Supplies

S41-26 SP Power Systems Ltd Specification: 36kV Indoor Switchgear

S41-27 SP Power Systems Ltd Specification: 36kV Outdoor Switchgear

2.2.5 ADDITIONAL REQUIREMENTS

The Tenderer shall give an undertaking that the switchgear and associated equipment offered will be identical in all essential particulars as regards design, material, place of manufacture and workmanship with switchgear and associated equipment previously supplied or covered by type registration tests, as set out in the relevant standards. Should the Tenderer be unable to give this undertaking the following sub-clauses will apply -



(a) Where the Tenderer proposes to supply switchgear and associated equipment not strictly in accordance with the aforementioned, the Employers Representative will consider giving registration to alternatives on an individual Contract basis provided that :-

(i) The equipment offered is of a design which has undergone type tests by a recognised authority in which case full details of such testing shall be submitted with the tender.

Or

(ii) Where such independent testing and registration has not taken place the Tenderer shall provide full technical details of any functional and environmental testing to which the equipment has been subjected.

It is the Employers preference that existing proven designs are offered except where a new design can be proven to be more technically & economically advantageous.

Alternatively, if a Tenderer wishes to offer switchgear and associated equipment of a new design, or incorporate any change which may in any way modify or affect the characteristics or performance of the System they shall advise the Employers Representative in writing so that arrangements can be made to obtain registration for incorporation in the Works.

Where the equipment supplied under this specification interfaces with equipment supplied by others or is existing, the successful tenderer shall provide the necessary resources to support the requirements of integration testing.

Where the switchgear and associated equipment has been previously approved or is covered by type registration tests, as set out in the relevant standards, the Tenderer need only state the manufacturer and the type reference number in the schedules contained in Part 5 of this specification. In addition they shall state the type registration number or the contract where the equipment has been previously approved. If any data in the schedules has been changed since the equipment was registered or previously supplied, the tenderer shall complete the schedule in full.

2.3 SWITCHGEAR RATED AT 145KV, 300KV AND 420KV

For 145kV, 300kV and 420kV switchgear, the technical requirements shall comply with NGTS 2.2, as modified by SP Power Systems document NG-12-043.

2.3.1 Circuit Breaker and Switches

Circuit breakers rated at 145kV, 300kV and 420kV shall comply with NGTS 3.2.1, as modified by SP Power Systems document NG-12-034 and shall be fitted with condition monitoring in accordance with SP Power Systems specification number SWG-03-019.



2.3.2 Disconnectors and Earthing Switches

Disconnectors and earth switches shall comply with NGTS 3.2.2, as modified by SP Power Systems document NG-12-038.

2.3.3 Surge Arresters

Surge arresters shall comply with NGTS 3.2.3, as modified by SP Power Systems document NG-12-039.

Surge arrester monitoring equipment shall comply with SP Power Systems specification number EPS-03-029.

2.3.4 Current Transformers

Current transformers shall comply with NGTS 3.2.4, as modified by SP Power Systems document NG-12-012.

2.3.5 Voltage Transformers

Voltage transformers shall comply with NGTS 3.2.5, as accepted by SP Power Systems document NG-11-044.

2.3.6 Current and Voltage Measurement Transformers

Current and voltage measurement transformers shall comply NGTS 3.2.6, as modified by SP Power Systems document NG-12-013.

2.3.7 Bushings

Bushings shall comply with NGTS 3.2.7, as accepted by SP Power Systems document NG-11-045.

2.3.8 Line Traps

Line traps for the use on the 275kV and 400kV systems shall comply with NGTS 3.2.8.

2.3.9 Post Insulators

Post Insulators shall comply with NGTS 3.2.9, as accepted by SP Power Systems document NG-11-046.



2.4 33KV SHUNT REACTOR CIRCUIT BREAKERS

33kV circuit breakers used shunt reactor switching shall be rated at 72.5kV and shall comply with NGTS 1 as modified by SP Power Systems document NG-12-040, NGTS 2.2, as accepted by SP Power Systems document NG-11-043 & NGTS 3.2.1, as modified by SP Power Systems document NG-12-034.

2.5 36KV RATED SWITCHGEAR

The technical requirements of indoor switchgear shall comply with S41-26 and outdoor switchgear shall comply with S41-27. Parts 3 and 4 of this specification shall take precedence over any non-technical references in these specifications. Where there is a technical conflict, S41-26 and S41-27 shall take precedence.

Copies of specifications S41-26 and S41-27 are available from the Employer.

Non-linear resistor type gapped surge arresters shall comply with BS EN 60099-1 and metal-oxide surge arresters without gaps shall comply with BS EN 60099-4.

2.6 25KV AC SINGLE PHASE SWITCHGEAR AND ANCILLARY EQUIPMENT

The technical requirements of the switchgear and ancillary equipment shall comply with Engineering Recommendation P.24.

Parts 3 and 4 of this specification shall take precedence over any non-technical references in these specifications. Where there is a technical conflict, P.24 shall take precedence.

SF6 gas service terminations shall be self sealing couplings of DILO size DN20 or HANSEN type B6K31-BS.


2.7 12KV RATED SWITCHGEAR

The technical requirements of indoor switchgear shall comply with SP Power Systems specification S2. Parts 3 and 4 of this specification shall take precedence over non-technical references in these specifications. Where there is a technical conflict, S2 shall take precedence.




3 TRANSFORMERS AND REACTORS

3.1 GENERAL

3.1.1 Specification and Standards

Transformers and reactors shall comply with all parts of IEC 60076 and IEC 60289, SP Power Systems Ltd specifications, and National Grid Company (NGC) specifications. Compliance with other applicable IEC and BS specifications is also required.

Transformers and reactors should be designed for a minimum life of 45 years under system operating conditions. Bushings and Tap switches should be designed for a life of 40 years.

Where connection is made to the National Grid System (NGC) operating conditions that apply are those which pertain to NGC specification NGTS 1, and where connection is made to the Employers System the stated operating conditions for SP Power Systems Ltd shall apply (refer to the schedules at the beginning of Part 2).

In particular, the life and reliability of the transformer shall not be affected by high frequency electrical transient voltages and currents generated by switching operations.

Particular attention is required when the transformers and reactors are connected to gas insulated substations, and Tenderers are required to submit a report on the proposals for the protection of transformers and reactors in conjunction with the switchgear contractor to ensure that the transformers, reactors and associated switchgear operate satisfactorily together.

3.1.2 Applicable Standards

Copies of the NGC specifications can be obtained from:

National Grid Transco plc NGT House Warwick Technical Park Gallows Hill Warwick

CV34 6DA

Copies of SP Power Systems Ltd standards and documents can be obtained from: SP Power Systems Ltd New Alderston House, Dove Wynd, Strathclyde Business Park, Bellshill, Lanarkshire ML4 3FF.



References in the specification to such standards and other documents shall be understood to be references to the edition applicable 28 days prior to the latest date for submission of the tender, unless otherwise stated.

Extensive use is made of supporting specifications, and this is primarily based on NGTS specifications issued by the National Grid Company of the United Kingdom.

This Specification should be read in conjunction with the following documents:

International Standards

IEC 60076 Power Transformers (All Parts) IEC 60185 Current Transformers IEC 60214 On-Load Tap Changers IEC 60289 Reactors IEC 60354 Guide to Loading Transformers IEC 60529 Degree of protection for Enclosures

National Grid Technical Specifications

NGTS 1, as modified by SP Power Systems document NG-12-040 Overview of National Grid System NGTS 2.1, as modified by SP Power Systems document NG-12-041 Substations NGTS 2.3 Transformers and Reactors NGTS 2.12, as modified by SP Power Systems document NG-12-043 Substation Auxiliary Supplies NGTS 2.19, as modified by SP Power Systems document NG-12-035 Ancillary Light Current Equipment NGTS 3.1.2, as modified by SP Power Systems document NG-12-037 Substation Earthing NGTS 3.2.4, as modified by SP Power Systems document NG-12-012 Current Transformers for Protection and General use on the 132kV, 275kV, and 400kV systems. NGTS 3.2.7, as accepted by SP Power Systems document NG-11-045 Bushings for the National Grid System NGTS 3.3.1, as modified by SP Power Systems document NG-12-014 Insulating Oil NGTS 3.3.3 Co-ordinating gaps NGTS 3.12.3, as modified by SP Power Systems document NG-12-002 Substation LVAC Supplies

SCT 15 Site Commissioning Tests

Electricity Association Technical Specifications


BEBS-T2 (1966) Specification for Transformers and Reactors



3.1.3 Enclosures and Small Wiring

Enclosures and small wiring shall be in accordance with NGTS 2.19, as modified by SP Power Systems document NG-12-035

Wiring shall be clearly numbered, and where existing wiring is in situ, the wire numbering shall comply with the existing numbering system. Tenderers shall include details of small wiring terminations and connection blocks used for CT and VT connections.

Tenderers shall submit all details of proposed enclosures, wiring, and wiring numbering system for approval by the Employer at the tender stage.

Voltage free, separate contacts shall be provided for every alarm and trip at the transformer main marshalling kiosk.

3.1.4 Protection Current Transformers

Unless specified within Part 1 of this document, the proposed protection CTs shall be designed and supplied by another contractor who shall arrange for delivery to the transformer manufacturers works. The successful Tenderer shall fit the CTs to the transformer prior to any testing of the main unit. The successful Tenderer shall ensure that the CTs have been fitted in the correct sequence and position and that they have not been damaged during transportation or installation.

3.2 DOUBLE-WOUND AND AUTO TRANSFORMERS

3.2.1 Introduction

This Section covers the supply, delivery and erection of double-wound transformers and autotransformers for connection to the Employers transmission/distribution system.

The foundations for the transformer will be prepared under a separate contract.

Connections to the transformers and switchgear will also be completed under a separate contract.

The transformers shall be manufactured in accordance with National Grid Technical Specification NGTS 2.3 and IEC 60076 except where modified by this specification.



3.2.2 General

Transformers shall be of three-phase construction mounted in a single tank. Transformers shall preferably be designed on the basis of a three-limbed core.

Transformers shall be designed with particular attention to the suppression of harmonics, especially the third and fifth, so as to minimise interference with communication circuits.

The maximum flux density in any magnetic component under any condition of voltage and frequency specified in Sections 3.5 to 3.23 of Part 2, and under all operating conditions specified shall not exceed 1.9 Tesla. Transformers shall not over flux under any of the operating conditions specified.

3.2.3 Rating

The rating of the transformer as specified can be achieved by the application of ONAN, ONAF and OFAF designs. The Tenderer is requested to offer the solution that offers the best economic offer to The Employer.

Where a noise enclosure is specified by the Tenderer to limit noise levels, the continuous maximum rating, as stated in the schedules in Part 1, shall apply when the transformer is installed within the noise enclosure.

The transformer shall be capable of the emergency cyclic loading, as appropriate, without exceeding a hot spot temperature of 120C a t an ambient air temperature of 10C, as follows.

(a) auto-transformers without tappings and all double wound transformers: 6 hours at 1.3 pu rating followed by 18 hours at 0.78 pu rating

(b) auto-transformers with tappings: 6 hours at 1.2 pu rating followed by 18 hours at 0.72 pu rating

Tenderers are requested to provide the estimated hottest spot temperature for either of these loading conditions in Part 5.

The transformer shall have a short time emergency (30 minute) rating of 1.5 p.u. and this shall be apply to the complete unit including bushings and tap changers.

3.2.4 Voltage Variation

3.2.4.1 Double Wound Transformers

Tappings are required to regulate the voltage appearing at the 33 or 11kV terminals of the transformer, as set out in the schedules in Part 1. Taps will be used to compensate for transformer and system voltage regulation and voltage variations, unless otherwise specified.



3.2.4.2 Autotransformers

Tappings are required to regulate the voltage appearing at the 132kV terminals of the transformer, as set out in the schedules in Part 1. Taps will be used to compensate for transformer and system voltage regulation and voltage variations, unless otherwise specified.

In cases where a 33kV tertiary winding is provided for auxiliary supplies and/or reactive control purposes, automatic voltage control of the 33kV output may be required. If 33kV tertiary voltage control is specified in Part 1, suitable options include the provision of line end tap changers, or neutral end tap changers with suitable booster transformers installed in the 33kV connections. The Tenderer shall clearly state the preferred method in the offer.

3.2.5 Losses and Impedance

The guaranteed losses on normal tapping, at normal frequency, and at Continuous Maximum Rating (CMR) shall be entered in the schedules in Part 5.

The formulae for economic assessment of losses are attached in Section 3.23.

No positive tolerances shall be allowed on guaranteed parameters.

For double wound transformers, the value of impedance between HV and LV windings shall lie within the appropriate envelope as shown on Drawing CAT3882SPL019778 attached.

For autotransformers, the value of impedance between HV and LV windings shall lie within the appropriate envelope as shown on Drawing 00175414 attached.

3.2.6 Windings, Connections and Terminations

Attention is drawn to NGTS 2.3/3.9.1, which specifies that insulation may be graded, and the arrangement of neutral connections.

Windings shall be designed to reduce to a minimum the out-of-balance forces inherent in the transformer. Tappings shall be arranged at such positions on the windings as will preserve, as far as possible, electro-magnetic balance at all voltage ratios.

Coils shall be constructed to avoid abrasion of the insulation under all operating conditions. The insulation on conductors between turns in direct contact with each other shall be paper. Netted polyester CTC may be used where agreed with the Employers Representative.

Tappings shall not be brought out from the inside of a coil or from intermediate turns.



The current ratings of HV and LV bushings shall be in accordance with the ratings given in the schedules in Part 1, and comply with NGTS 3.2.7., as accepted by SP Power Systems document NG-11-045.

Bushings on the transformer shall be mounted on conventional turrets that shall have accommodation for current transformers in accordance with the schedules.

A test loop shall be fitted to all turrets equipped with bushings of 145kV or greater, to enable primary current injection testing to be made (refer to drawing GEN3813SPL019610). The rating and other details of test loops are given in NGTS 2.3/3.17.

Where dual vector groups are specified in Part 1, easily accessible suitable change over links shall be provided to enable selection of the required vector group.

Where the transformer being specified is a star connected HV, double wound with a lower voltage delta connected winding no greater than 36kV, the HV neutral shall be brought out to a single bushing for earthing directly. Separate neutral bushings are required on all autotransformers.

3.2.7 Condition Monitoring

All transformers require suitable condition monitoring equipment to be fitted in line with the following requirements.

A 4-20mA isolated current loop output capable of interfacing with the Employers SCADA system or with the local Substation Control System shall be fitted to the following pieces of equipment, detailed elsewhere in this specification.

(a) Winding temperature instruments on all windings. (b) Top oil temperature instrument. (c) Buchholz relay gas level instrument.

An isolated binary digital output of tap position is required from each tap changer in addition to the output to the remote standby control panel if specified.

All outputs should be routed via the marshalling kiosk.

Future provision for a Hydran gas in oil monitoring device or similar is required and shall comply with NGTS 2.3/3.17 The Hydran device will not form part of this contract.

Three dielectric windows are required on the transformer lid. Windows should be non-metallic and capable of withstanding the temperature, pressure and environmental aspects of their location. Typical windows should be 150mm in diameter and located in positions to maximise their effectiveness as agreed with the Employer. It is not intended to fit UHF couplers initially and the windows require to be fitted with a metallic cover until required.



Fibre optic point sensors to measure winding hottest spot temperatures may require to be fitted in the HV and LV windings. The Tenderer shall state the additional cost of this system in Part 6.

Full details of the method of insertion of the sensors and of the verification of the location of the sensor shall be included in the Tender. The location of any sensors provided shall be agreed with the purchaser before installation.

A performance bond will be required to cover the unsatisfactory operation of any of the Fibre Optic Probes specified and fitted at agreed locations and which do not provide a reasonably accurate temperature analogue output during testing and on completion.

3.2.8 Core and Support Structure Earthing

Where the magnetic circuit is divided into packets connection straps shall be provided between packets to avoid any flashover between core packets during impulse testing.

Appropriate Test levels for core insulation systems in air and oil are given in the schedules in Section 3.22.

3.2.9 Tap Changer

An on-load tap changer, complying with IEC 60214, shall be provided where specified in Part 1.

Contrary to NGTS 3.3.4, where an in-tank tap changer is offered barrier boards and full separation of tap changer and main tank oil is not required.

NGTS 3.3.4 implies that the tap changer should be of the separate selector and diverter switch type, fitted in separate oil compartments to facilitate condition monitoring of the selector switches. For applications with primary windings at 132kV and below, this clause does not preclude the tender from offering tap changers with combined selector/diverter switches fitted in a single compartment.

The tap changer shall be capable of operating for power flows from HV to LV and from LV to HV without affecting the transformer rating.

The tap change control circuits will be required to comply with standard control schemes for SP Power Systems Ltd or for the National Grid Company (NGC). The type of control scheme required is specified in the schedules in Part 2, Section 3 of this document.

Tap changers shall be capable of Remote/Local operation from a control scheme supplied by others, unless otherwise specified in Part 1 of this document.

The tap change control supply shall be from the 110 V AC substation supplies and the drive mechanism shall normally be 400 V three-phase. Tap changer designs that utilise a single-phase motor are acceptable



A manual tap changer operating handle is required, arranged so that the motor drive is automatically rendered inoperative when the handle is inserted.

Mechanical indications of tap position number, tap change complete and the total number of tap-changes are required in the motor drive cubicle.

Where the selector compartment is not part of the main transformer oil system, a separate gas and oil actuated relay is required to be fitted in the pipework between each selector tank and the conservator.

An oil surge relay is required for each tap-changer diverter compartment.

All motor drive circuits shall be provided with a thermal overload protection device. A means shall be provided to enable the motor protective switch to be electrically tripped from a remote point. A clean contact is required to indicate at a remote point that a tap change is in progress or to drive a tap change incomplete alarm.

A means for remote tap position indication is required, this is normally of the resistive transducer potentiometer type although alternatives may be offered. Additionally, two auxiliary tap position indicating transducers (selective tap position indicator switches) are required, each consisting of a single pole switch with one contact for each tap position.

3.2.10 Tanks

Tanks and coolers shall be capable of withstanding full vacuum. The manufacturer shall state the guaranteed maximum permanent deflection in the schedules.

Tanks shall not permanently distort, or cause cracking of stiffener welds, when lifted or hauled on site.

Coolers may be offered as separate cooler banks, tank mounted frames with separate manifolds, or direct mounted radiators. Coolers should be capable of being isolated from the rest of the oil system by the use of suitable valves.

Where a separate cooler bank is offered, it shall be capable of being installed at either end of the transformer by the provision of suitable blanked mounting flanges.

Facilities to enable the transformer to be hauled or slewed in any direction shall also be provided. A design that requires slide rails to be placed in discrete positions or utilises a detachable under base is not acceptable.

The complete transformer, as arranged for transport, shall be capable of being lifted without undue strain on the tank or its stiffeners.

Transformers shall be suitable for transportation as set out in NGTS 2.3/3.1.4.



Tank covers shall not permanently distort when lifted. Inspection openings of adequate size shall be provided to give access to bushings, winding connections etc. Inspection covers shall be provided with lifting handles and not exceed 25 kg in weight.

Tanks, conservators, pipe work etc. shall be cleaned by an appropriate means and given two coats of oil and weather resistant paint. The final coat should be a gloss finish, Admiralty Grey in colour (Shade no. 632) as specified in BS 381C is preferred, although manufacturers may offer alternative colours which are economically advantageous to The Employer. The internal surfaces of the marshalling kiosk and the tap changer motor drive cubicle shall be painted white. Any departures form these colours, if required by the Employer, shall be detailed in Part 1 of this document.

Load bearing welds shall be shown to be free from significant defects by Magnetic Particle Inspection. Oil retaining welds should be checked by non-destructive testing methods to ensure integrity. The level of weld checks shall be agreed between the Contractor and the Employer.

3.2.11 Fittings

The fittings shall be compliant with NGTS 2.3/3.17, items (a) to (z), except where modified by this specification.

Oil preservation systems approved by the Employer may be offered in lieu of the refrigerating type dehydrating breather. Any breather supplied as part of an oil preservation system shall be fitted with a silica gel breather.

In addition to the NGC standard fittings a blanked off pipe flange, accessible from ground level, shall be provided to facilitate the fitting of a silica-gel breather in the event of failure of the refrigeration breather.

Unless otherwise specified in Part 1, co-ordinating gaps are not required. Transformers for use on the Employer systems will be fitted with suitable surge arresters on all external terminals. A facility for suitable tank mounted fixings for surge arresters is required as an option, but the surge arresters shall be supplied and fitted under a separate contract.

Transformers supplied to the Employer do not require an owners serial number i.e. T number.

3.2.12 Noise Preventative Works

The maximum sound power level measured in accordance with IEC 60076 for auto-transformers with 275kV or 400kV primary windings shall not exceed 87dB(A). This limit shall apply to both the main transformer and any associated cooling equipment.

Where the primary winding is 275kV or less, for double wound transformers, the maximum sound power level measured in accordance with IEC 60076 shall not exceed 77dB(A) for the main transformer and 87dB(A) for associated cooling equipment.



The Tenderer shall enter the average guaranteed surface noise in the schedules in Part 5.

In some cases, site specific noise levels are required which are lower than those specified above. Where site specific noise levels are to apply, the lower level required will be detailed in Part 1. The Tenderer will clearly state how the noise levels specified will be met. Acceptable methods include low noise designs, standard design plus noise enclosure, active noise control systems or a combination.

Where a noise enclosure is offered the arrangement shall be generally in accord with NGTS 2.3/3.14.2.

The Employer requires that all drawings of the proposed enclosure should be submitted for approval. Drawings should show the arrangement of bushing turrets, weatherproofing, terminal bushings and boxes, paperwork, and kiosk.

3.2.13 Pressure Relief Device

Pressure relief devices shall be in compliance with NGTS 2.3/3.17.

Oil ducting shall be provided to vent oil at a height of 1m above ground level. The diameter of the ducting shall not cause incorrect operation of the device. A suitable warning label shall be provided.

The position of all multicore cables shall be indicated on a drawing and submitted to the Employer during the design phase for comment.

3.2.14 Valves

Valves for oil circuits shall be full-way gate valves except that, for valve sizes 100 mm to 300 mm, cam-locking butterfly valves may be offered.

Pipe work and valves shall be compliant with NGTS 2.3/3.3.

Valves shall be provided with open/shut indication and facilities for locking in either position.

3.2.15 Cooling Plant

The cooling medium is air, unless otherwise stated in the schedules in Part 1.

Coolers shall be compliant with NGTS 2.3/3.3. Tenderers should note that pumps are not mandatory. Contrary to NGTS 2.3/3.3 radiators that are hot dipped galvanised do not require to be painted unless a painted finish is specified in Part 1. Where a paint finish is specified, the paint system shall provide the lifetime protection of the radiator, without the need for galvanising.

Natural and forced cooling ratings shall be stated in the schedules in Part 1.



3.2.16 Insulating Oil

The equipment shall be supplied complete with the first filling of insulating oil for testing and commissioning.

The oil shall be unused naphthenic based and comply with the requirements of National Grid Company Technical Specification NGTS 3.3.1., as modified by SP Power Systems document NG-12-014.

3.2.17 Winding Temperature Indicators

Winding Temperature indicators shall be compliant with NGTS 2.3/ 3.4.1 (instruments) and 3.4.2 (Ammeters for calibration and test).

In addition to the WTI indicators specified in NGTS 2.3 a top oil temperature instrument is required. WTIs and OTIs require to be capable of remote indication.

3.2.18 Marshalling Kiosk

A weatherproof marshalling kiosk (MK) sh

SP Power Systems Ltd - Part 2 - Standards

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