DUE Mar16 rev2.pptx

8/15/2019 DUE Mar16 rev2.pptx

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In association with:

Speaking of Risks: An Update

to the NRS097-2 and other Technical Requirements

(SSEG)

Background to SSEG

Specification Development

Dr Gerhard Botha

2016/03/31


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Overview

• Background to SSEG in South Africa

• Inverter Specifications

• Small Generator Specifications

• Planning Framework

• Type Testing

• Policies and Procedures

• Installation Standards

• Tariffs


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Background

• Small Scale Embedded Generation

• SA development since 2007

• Municipalities received many requests for solar PVinstallations

• Approached Eskom for unified requirements viaNRS

• First edition published Dec 2010 – Based on IEC61727

• NERSA “approval” of such installations formunicipalities in Sep 2011 – Municipalities need to keep proper records and

report to NERSA, what, where, how much etc.;

– Comply with requirements from NRS 097-2-1;


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Background

• Then happened load-shedding…

• Co-generation

• Tariff

• Requirements – Eskom response via internal

standard• “Distribution standard for the interconnection of

embedded generation”

• Minimum technical and statutory requirements forthe connection of embedded generators tomedium-voltage and high-voltage utilitydistribution networks

• MV and HV


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NRS 097

• Grid interconnection of embeddedgeneration

• Part 1: Distribution standard for the

interconnection of embedded generation – To be based on Eskom standard

• Still undeveloped…

•

>100kVA• SA Grid Code for Renewable Power

Plants (RPP Grid Code)


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NRS 097-2

• Grid interconnection of embedded generation

• Part 2: Small-scale embedded generation

• Section 1: Utility interface

–Technical requirements for a generator toconnect to the utility network

– Not an inverter specification“Device Independent”

– Not a generator specificationInterface Document

– Describe the requirements at the utility interface


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NRS 097-2

• Connected to LV (


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Section 1 New Additions

• Controllability requirements

– Larger than 100kVA

• Ramp-up after abnormal conditions

• Communication requirements

– Need local control

–

Number of installations cannot be individuallycontrolled


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• Power factor requirements updated

• A1 and A2 pf > 0.98

• A3 pf > 0.95

• May operate anywhere in the shaded region


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• Safety disconnect requirements

• Abnormal Voltages

Voltage range(at point of connection) Maximum trip timeS

V < 50 % 0,2 s

50 % ≤ V < 85 % 10 s

85 % ≤ V ≤ 110 % Continuous operation

110 % < V < 115 % 40 s

115% ≤ V < 120% 2 s

120 % ≤ V 0,16 s

NOTE If multi-voltage control settings are not possible, the more

stringent trip time should be implemented, e.g. 2 s between 110%

and 120% of voltage.


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• Safety disconnect requirements

• Abnormal Frequency


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• Ride-through requirements (Also RPP Grid

Code)

– Category A1 and A2

– Dip type Y and X1 (NRS 048-2)

20s

120%

110%

90%Y

80%

Z1

S

70%

X160%

X2

Z2

40%

T

0%150 600 3000 ms


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• Ride-through requirements (Also RPP Grid

Code)

– Category A3

– Same as category B (and C excluding Area D)

20s

110%

120%

150 600 3000 ms

40%

0%

60%

Y

Z1

SX1

X2

Z2

T

70%

80%

90%

Area A

Area B

Area C

Area D


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• Power Quality

• Limits for flicker and voltage unbalance

• Pst = 0,35;

• Plt = 0,30;

• Maximum unbalance between phases

– < 4.6 kVA

– Two- and three-phase connections


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• EMC

• Smart meter and residential equipment

interference

• SANS/IEC 50065-1

• CISPR 11 Class B


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• Fault Level

5th percentile of MV


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NRS 097-2

• Section 3: Simplified utility connection criteria for low-voltage connected generators

• For use by utilities – Customers can establish what would be easy to connect,

e.g. smaller than 25% of ADMD/Breaker size

– Maximum size as a function of cable parameters anddistance from transformer

• Flowchart to consider connection without detailedstudies

• When SSEG connection request complies with simplifiedchecks, can be connected

• Principle of fairness

• Eskom would not allow all these connections at this time – Pilot project (dedicated connections)


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NRS 097-2

• VDE 4105 stipulates 3% max voltage

rise due to all SSEG connected

– Implicit in planning flowchart


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Voltage profiles with no generation

Low load1% rise

limit

Peak load

15% drop

limit

105

104.5

109

108

90

90

95

100

105

110

0 5

V o l t a g e ( % )

Distance (km)


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Voltage profiles with generation

105

102

103.5

96.5

105 106.5

112.5

114.5

95

97.5

100

102.5

105

107.5

110

112.5

115

V o l t a g e ( %

)

Distance (km) peak loadlow load

Network can absorb significantly less power than it can supply


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NRS 097-2

• Part 2: Embedded generator requirements – Type Testing

• How to prove the generator complies with requirements ofpart 1

• DRAFT

•

Review international standards again – International exposure• No single document that will fulfil the requirements for SSEG

connection and type testing for LV networks in South Africa• Specific comparison for utility interface:

– VDE 4105

– EN 50438

–IEC 61727, 61000-series, other

– ER G83/1-1 and G59/2

– IEEE 1547 / UL 1741

• Align with international best practices!


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NRS 097-2

• Section 4: Procedures for

implementation and application

• To be developed…


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SA Grid Code

• RPP Grid Code

• Category A – A1: 0 -13.8kVA (4.6kVA/phase)

–

A2: 13.8-100kVA – A3: 100kVA – 1MVA (including smaller units

connected to a dedicated MV/LVtransformer)

• Category B – 1MVA – 20MVA

• Category C – Larger than 20MVA


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SANS: Wiring Code

• SANS 10142-3 WG convened

• Progress slow

– Utility viewpoint

– Installers viewpoint


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Licensing

• Feedback received yesterday


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Safety Concerns

• Installation deficiencies – Installation of utility-accessible lock-out breaker (where feasible)

– Such a breaker is not feasible in shared networks

– DC fed back into network (possible failure modes of the inverter)

– DC vs. AC breakers and associated derating

• Anti-islanding – Failure to disconnect when the network is de-energised

– Test for voltage before work commences will safeguard LV personnel

• Re-connection while maintenance in progress – Failure of the inverter to detect that the network is not energised

– Remains a risk (in shared networks) until LV networks can be earthed

– Earthing at LV requires redesign of LV networks (e.g. providing earthing terminalsetc.)

• LV Maintenance Process –

Need to measure after disconnection – Most voltmeters either DC or AC

• Australia – rumours of several PV installations that caused fires atresidential homes

• Emergency Personnel, e.g. firefighting

2016-04-02 28


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How to earth a

generator


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Few Other Aspects

• No approved tariffs

– Cowboy approach – under the radar

• Offset of consumption

– Gives good return on investment

• Licensing vs. registration

– Regulatory framework

• Power Quality – RPP GC

– Default values for Generators < 5MVA


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Subtleties

• Renewable Power Producers

– Point of Connection

• Embedded Generators

– Generator terminals

– Point of Connection

• Safety aspects


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Conclusions

• South Africa has learnt a lot

• Alignment with international best

practices as far as possible

• BUT: South African Networks and

Conditions are completely different to

typical European or American networks


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Thank you

[email protected]

+27 83 407 9651

DUE Mar16 rev2.pptx

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