Reference Manual CU1 Reference Manual.pdffrom OMICRON electronics is a surge arrestor unit protecting the operating staff and equipment from high-voltage hazards during measurements

CP CU1

Reference Manual

COUPLING UNIT FOR LINE IMPEDANCE

AND K FACTOR MEASUREMENTS,

COUPLING MEASUREMENTS ON POWER

LINES AND SIGNAL CABLES AND

GROUND IMPEDANCE MEASUREMENTS

OF LARGE SUBSTATIONS

V 1.4

2

CP CU1 Reference Manual V 1.4

Article Number VESD0671 - Manual Version: CPCU1.AE.4

© OMICRON electronics 2005. All rights reserved.

This Reference Manual is a publication of OMICRON electronics GmbH.

All rights including translation reserved. Reproduction of any kind, e.g., photocopying, microfilming or

storage in electronic data processing systems, requires the explicit consent of OMICRON electronics.

Reprinting, wholly or in part, is not permitted.

This Reference Manual represents the technical status at the time of printing. The product information,

specifications, and all technical data contained within this Reference Manual are not contractually

binding. OMICRON electronics reserves the right to make changes at any time to the technology and/or

configuration without announcement. OMICRON electronics is not to be held liable for statements and

declarations given in this Reference Manual. The user is responsible for every application described in

this Reference Manual and its results. OMICRON electronics explicitly exonerates itself from all liability

for mistakes in this manual.

3

Contents

Contents

Using This Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

Operator Qualifications and Safety Standards. . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Conventions and Symbols Used . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Related Documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Safety Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Operating the Measurement Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Orderly Measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Disclaimer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1 Hardware Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

1.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

1.2 Circuit Diagram of CP CU1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

1.3 Operating Controls of CP CU1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

1.4 CP CU1 Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

1.5 CP GB1 Grounding Box. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

1.5.1 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

1.5.2 Shorting the Phases. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

1.5.3 Changing the Surge Arrestors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

1.6 Clamp-on Ammeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

2 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

2.1 Measurement Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

2.2 Operating Principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

2.3 Configuring CPC 100 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

2.4 Setting CP CU1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

3 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

3.1 Template Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

3.2 Safety Instructions for Connecting CP CU1 to Power Lines . . . . . . . . . . . . . . . 26

3.2.1 Before Starting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

3.2.2 Recommended Current Range Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

3.2.3 Estimating the Open-Line Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

3.2.4 Connecting the Measurement Setup to Power Lines. . . . . . . . . . . . . . . . . . . 28

3.3 k Factor Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

3.3.1 Why k Factor Measurement? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30


4

3.3.2 Performing Measurements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

3.3.3 Interpretation of Measurement Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

3.4 Ground Impedance and Step Voltage Measurement. . . . . . . . . . . . . . . . . . . . . 39

3.4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39


3.4.3 Interpretation of Measurement Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

3.5 Measurement of Coupling into Signal Cables . . . . . . . . . . . . . . . . . . . . . . . . . . 45

3.5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45


4 Technical Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51

4.1 CP CU1 Output Ranges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

4.2 CP CU1 Measuring Transformers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

4.3 CP CU1 Inputs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

4.4 CP GB1 Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

4.5 Output Power. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

4.6 Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

4.7 Environmental Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

4.8 Mechanical Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

4.9 Clamp-on Ammeter (Accessory) Specifications. . . . . . . . . . . . . . . . . . . . . . . . . 54

Contact Information / Technical Support . . . . . . . . . . . . . . . . . . . . . . . . . .55

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57

5

Using This Manual

Using This Manual

This Reference Manual provides detailed information on how to use the CP CU1

coupling unit safely, properly and efficiently. The CP CU1 Reference Manual

contains important safety instructions for working with CP CU1, gets you familiar

with operating CP CU1, and provides typical application examples. Following

the instructions in this Reference Manual will help you to prevent danger, repair

costs and possible down time due to incorrect operation.

The CP CU1 Reference Manual always has to be available at the site where

CP CU1 is used. It must be read and observed by all users of CP CU1.

Reading the CP CU1 Reference Manual alone does not release you from the

duty of complying with all national and international safety regulations relevant

to working with CPC 100 and CP CU1. The regulation EN 50191 "The Erection

and Operation of Electrical Test Equipment" as well as all the applicable

regulations for accident prevention in the country and at the site of operation has

to be fulfilled.

Operator Qualifications and Safety Standards

Working on overhead lines is extremely dangerous. Testing with CP CU1 must

be carried out only by qualified, skilled and authorized personnel. Before starting

to work, clearly establish the responsibilities. Personnel receiving training,

instructions, directions, or education on CP CU1 must be under constant

supervision of an experienced operator while working with the equipment.

Testing with CP CU1 must comply with the relevant national and international

safety standards listed below:

• EN 50191 (VDE 0104) "Erection and Operation of Electrical Equipment"

• EN 50110-1 (VDE 0105 Part 100) "Operation of Electrical Installations"

• IEEE 510 "IEEE Recommended Practices for Safety in High-Voltage and

High-Power Testing"

• LAPG 1710.6 NASA "Electrical Safety"

Moreover, additional relevant laws and internal safety standards have to be

followed.


6

Conventions and Symbols Used

In this manual, the following symbols indicate paragraphs with special safety

relevant meaning:

Related Documents

The following documents complete the information covered in the CP CU1

Reference Manual:

Symbol Description

Equipment damage or loss of data

possible.

Personal injury or severe damage to

objects possible.

Title Description

CPC 100 User Manual Contains information on how to use

the CPC 100 test system and

relevant safety instructions.

CPC 100 Reference Manual Contains detailed hardware and

software information on CPC 100

including relevant safety instructions.

7

Safety Rules

Safety Rules

Before operating the CP CU1 coupling unit, read the following safety rules

carefully. If you do not understand some safety rules, contact OMICRON

electronics before proceeding. CP CU1 is designated for use with the CPC 100

test system. Therefore observe the safety rules both in this Reference Manual

and in the CPC 100 User/Reference Manual when working with CP CU1.

Depending on the application and the device under test, specific safety

instructions must be observed. Very often the danger coming from the device

under test is even higher that the danger from CP CU1 itself. For application

specific safety instructions, see 3.2 "Safety Instructions for Connecting CP CU1

to Power Lines" on page 26.

General

Always observe the five safety rules:

• Disconnect completely

• Secure against re-connection

• Verify that the installation is dead

• Carry out grounding and short-circuiting

• Provide protection against adjacent live parts

Do not touch any terminals without a visible connection to ground.

Before handling CP CU1 or CPC 100 in any way, connect them with a solid

connection of at least 6 mm2 cross-section to ground. Ground CP CU1 as close

as possible to CPC 100.

Use the CP GB1 grounding box to connect CP CU1 to overhead lines and power

cables. For detailed information, see the application specific 3.2 "Safety

Instructions for Connecting CP CU1 to Power Lines" on page 26.

When using CP GB1, ground it near the place where the connection to the test

object is made. Make sure that the grounding stud is in good condition, clean

and free of oxidation.

Make sure that all studs and cables of CP GB1 are screwed tight.

Make sure that the test object’s terminals to be connected to CP CU1 do not

carry any voltage potential. During a test, the only power source for a test object

may be CP CU1 (powered by CPC 100). The only exception are measurements

on overhead lines as described in 3 "Applications" on page 25.

Do not open the CP CU1’s or CP GB1’s housing.


8

Do not repair, modify, extend, or adapt CP CU1, CP GB1 or any accessories.

Use only original accessories available from OMICRON electronics.

Use CP CU1, CP GB1 and their accessories only in a technically sound

condition and when its use is in accordance with the regulations. In particular,

avoid disruptions that could in turn affect safety.

Do not use CP CU1 if you have a cardiac pacemaker. Before operating CP CU1

make sure that there is no person with a cardiac pacemaker in the immediate

vicinity of the measurement setup.

Operating the Measurement Setup

Before operating CP CU1, CPC 100 and, when used, CP GB1, ground them as

described in "General" on page 7.

When using CP GB1, ground it near the place where the connection to the test

object is made. Make sure that the grounding stud is in good condition, clean

and free of oxidation.

Life threatening voltages up to 600 V can appear on all CP GB1’s contacts and

on all clamps and cables connected to CP CU1 during the test. Keep safe

distance from them.

Before handling CP CU1 or CP GB1 in any way (even before setting the current

range switch), make sure that the device under test (e.g. overhead lines or

power cables) are well grounded (e.g. by closing the grounding switch) near the

measurement setup.

Power CP CU1 only from the CPC 100’s EXT. BOOSTER output. Use only

booster cables supplied by OMICRON electronics.

Ensure that the short-circuit bar is always plugged in the CP CU1’s I AC output

whenever the output is not connected to the I AC input of CPC 100.

Connect the CP CU1’s I AC output exclusively to the I AC input of CPC 100.

Before connecting CP CU1 with CPC 100, turn off CPC 100 either by the

POWER ON/OFF switch or the Emergency Stop button.

Set the current range switch on the CP CU1’s front panel only when CPC 100 is

turned off and the test object is grounded.

In addition to the above safety rules follow the application specific 3.2 "Safety

Instructions for Connecting CP CU1 to Power Lines" on page 26.

9

Safety Rules

Orderly Measures

The CP CU1 Reference Manual or alternatively the e-book in PDF format has

always to be available on the site where CP CU1 is being used. It must be read

and observed by all users of CP CU1.

CP CU1 may be used only as described in 3 "Applications" on page 25. Any

other use is not in accordance with the regulations. The manufacturer and/or

distributor is not liable for damage resulting from improper usage. The user

alone assumes all responsibility and risk.

Following the instructions provided in this Reference Manual is also considered

part of being in accordance with the regulations.

Disclaimer

If the equipment is used in a manner not specified by the manufacturer, the

protection provided by the equipment may be impaired.


10

11

Hardware Information

1 Hardware Information

1.1 Overview

CP CU1 is a coupling unit designated for measurements with the CPC 100 test

system mainly on overhead lines and power cables. Typical applications include

line and cable impedance measurements, measurements of k factors, mutual

coupling of power lines, measurements of coupling between power lines and

signal cables, and ground impedance measurements. The CP GB1 grounding

box (see 1.5 "CP GB1 Grounding Box" on page 14) available as an accessory

from OMICRON electronics is a surge arrestor unit protecting the operating staff

and equipment from high-voltage hazards during measurements on overhead

lines and power cables in case of unexpected events on the power line.

1.2 Circuit Diagram of CP CU1

Figure 1-1: "Circuit Diagram of CP CU1" below shows the principal circuit

diagram of the coupling unit.

Figure 1-1:

Circuit Diagram of

CP CU1

BOOSTER

Power transformer Current range switch

Voltmeter

CT

VT

I AC (0…2.5 A)

V1 AC (0…30 V)

I OUT (0…100 A)

V SENSE (0…600 V)

Surge arrestor

Surge arrestor

Fuse 30 A


12

1.3 Operating Controls of CP CU1

The front panel of CP CU1 provides the following functional elements:

• BOOSTER input for connecting with the CPC 100’s EXT. BOOSTER output

• Current range switch for setting the current range of CP CU1

• Voltmeter for measuring the voltage at the test object’s terminals

• I OUT current output

• I AC output for measuring the output current using a CT (current transformer)

with the 100 A : 2.5 A transformation ratio

The output is to be connected with the I AC input of CPC 100.

• V SENSE input for measuring the voltage at the test object’s terminals

• V1 AC output for measuring the voltage at the test object’s terminals using a

VT (voltage transformer) with the 600 V : 30 V transformation ratio

The output is to be connected with the V1 AC input of CPC 100.

• Short-circuit bar for shorting the I AC output whenever the output is not

connected to the I AC input of CPC 100

• Equipotential ground terminal for grounding CP CU1 close to the position of

the operating staff

Figure 1-2: "Front Panel" below shows the CP CU1’s functional elements.

Figure 1-2:

Front Panel Equipotential

ground

terminal

BOOSTER input

Current range

switch Voltmeter

Location to

store the short-

circuit bar

I AC output V1 AC output V SENSE input

I OUT output

Fuse 30 A

13


1.4 CP CU1 Accessories

The following accessories are delivered with the CP CU1 coupling unit:

Table 1-1:

CP CU1 Accessories

Accessories Description

Booster cable Power connection from the

CPC 100’s EXT. BOOSTER

output to the CP CU1’s

BOOSTER input

V1 AC coax. cable Connection from the

CPC 100’s V1 AC input to the

CP CU1’s V1 AC output

4 × Banana cable Connection from the

CPC 100’s I AC input to the

CP CU1’s I AC output and

connection from the CP CU1’s

V SENSE input to the Kelvin

clamps voltage sense outputs

2 × Kelvin cable Connection from the

CP CU1’s I OUT output to the

current feed-in point (usually

at CP GB1)

Grounding cable Connection from the

CP CU1’s equipotential

ground terminal to the

substation ground

Short-circuit bar A bar for shorting the

CP CU1’s I AC output when

the output is not connected to

the I AC input of CPC 100


14

1.5 CP GB1 Grounding Box

1.5.1 Description

The CP GB1 grounding box (see Figure 1-3: "CP GB1 Grounding Box" below)

is a surge arrestor unit for connecting CP CU1 to the test object. If high voltage

appears for a short time on the test object’s terminals, an arc discharges the

voltage and distinguishes without destroying the grounding box. If the arc

persists for a longer time period, the surge arrestor insulator melts and the

terminals are short-circuited to ground, thereby protecting the operating staff,

CP CU1 and CPC 100.

Figure 1-3:

CP GB1 Grounding Box

Caution: The CP GB1 grounding box must be used for measurements on overhead lines or power cables.

The CP GB1 grounding box is available for three different ground connection

types: cylindrical grounding studs of 16 mm diameter or ball studs of 20 mm and

25 mm (1 inch) diameter. The grounding socket clamp is needed for secure

ground connection of CP GB1 to the substation ground. The grounding socket

clamps compatible with the grounding studs in the substation are given in Table

Equipotential

ground stud

L2 line stud

B/L2/yellow

L1 line stud

A/L1/red

L3 line stud

C/L3/blue

Other stud standards

available optionally

15


1-2: "Grounding Studs and Socket Clamps" below. For ordering information,

contact OMICRON electronics sales office. When ordering CP GB1, choose one

connection set; additional connection sets are available optionally.

Table 1-2:

Grounding Studs and

Socket ClampsGrounding Stud in the Substation Proper Grounding Socket Clamp

16 mm cylindrical

grounding stud

16…20 mm grounding socket clamp

(shipped with the 16 mm cylindrical

and 20 mm ball CP GB1’s studs)

20 mm ball

grounding stud

25 mm ball

grounding stud

25 mm grounding socket clamp

(shipped with the 25 mm CP GB1’s

studs)

12 mm

16 mm


16

Caution: Depending on the type of grounding studs in the substation, the appropriate connection set and socket clamp have to be used. Connecting socket clamps of one type to a grounding point of another system is highly dangerous on both the connection of the grounding set to CP GB1 and the

connection of CP GB1 to the grounding point in the substation. The 16 to 20 mm socket clamps are designed and tested for fault currents up to 26.5 kA, the 25 mm (1 inch) socket clamp for fault currents up to 30 kA, both for a maximum duration of 100 ms. On locations where higher fault currents are possible, CP CU1 and CP GB1 must not be used.

Figure 1-4:

Screwing the CP GB1’s

Studs

For transportation, the CP GB1’s studs are usually removed. If this is the case,

mount them onto CP GB1 using the delivered wrench and screw them tight (see

Figure 1-4: "Screwing the CP GB1’s Studs" on page 16).

17


1.5.2 Shorting the Phases

A three-lead cable is delivered with CP GB1 for shorting all phases for

L1||L2||L3-E measurements (see Figure 3-5: "Zero-Sequence Impedance

Measurement" on page 34, Figure 3-8: "Ground Impedance and Step Voltage

Measurement" on page 41, Figure 3-13: "Measurement with the Loop Between

Parallel Lines and Ground" on page 48 and Figure 3-14: "Calibration with the

Loop Between Parallel Lines and Ground" on page 49).

Figure 1-5:

Three-Lead Cable

To short the phases, connect the line studs of CP GB1 as shown in Figure

1-6: "Shorting the Phases" below.

Figure 1-6:

Shorting the Phases


18

1.5.3 Changing the Surge Arrestors

The surge arrestors of CP GB1 can permanently short-circuit the CP GB1’s

terminals to ground if overvoltage appears on the terminals. Even short

transients can cause a discharge and, if the energy is too high, possibly damage

the surge arrestor. Defective surge arrestors can result in erroneous

measurement results. If the measurement results obtained using CP GB1 differ

considerably from the expected values, check the surge arrestors using

CPC 100 as follows.

Apply a voltage of 500 V for at least 10 seconds using the VWithstand test card

from the resistance test cards. Set a test current of 0.01 A. If the current is

exceeded, an error message is displayed. In this case the surge arrestor under

test is defective and you have to replace it. If no message is displayed, the surge

arrestor is intact. For detailed information on this test, see the CPC 100

Reference Manual. Repeat the test for all three studs A/L1, B/L2 and C/L3.

Replace defective surge arrestors only by spare parts from OMICRON

electronics (see Figure 1-7: "Surge Arrestors" below). For ordering information,

contact OMICRON electronics sales office.

Figure 1-7:

Surge Arrestors

Note: Before changing the surge arrestors, check whether there is a fault that caused the problem and remove it.

19


To replace a surge arrestor:

1. Disconnect CP GB1 completely and observe the five safety rules in "Safety

Rules" on page 7.

2. Open the surge arrestor chamber using a 22 mm wrench by removing the

contact screw (see Figure 1-8: "Opening the Surge Arrestor Chamber" on

page 19).

Figure 1-8:

Opening the Surge

Arrestor Chamber

3. Turn CP GB1 upright and move the stud over the surge arrestor chamber

until the surge arrestor falls out.

4. Replace the defective surge arrestor by the spare one.

5. Screw the contact screw very tight (torsional moment of 15…20 Nm).

Contact screw


20

1.6 Clamp-on Ammeter

A clamp-on ammeter for AC 50/60 Hz (see Figure 1-9: "Clamp-on Ammeter"

below) is available from OMICRON electronics as an accessory. For ordering

information, contact OMICRON electronics sales office.

Figure 1-9:

Clamp-on Ammeter

The clamp-on ammeter provides the following features:

• Hold function

• Battery check

• Auto power off

• Bar display

• Voltmeter

• Ohmmeter

• Contact check with beeper

21

Operation

2 Operation

2.1 Measurement Setup

The measurement setup consists of the CPC 100 test system, of the CP CU1

coupling unit and, in case of measurements on overhead lines and power

cables, of the CP GB1 grounding box. Figure 2-1: "Measurement Setup" below

shows the functional block diagram.

Caution: CP CU1 must be connected to the test object through the CP GB1 grounding box for measurements on overhead lines or power cables. For these applications, connect the measurement setup by following 3.2 "Safety Instructions for Connecting CP CU1 to Power Lines" on page 26.

Figure 2-1:

Measurement Setup

2.2 Operating Principle

CP CU1 is a coupling unit controlled by the CPC 100 test system via the

BOOSTER interface. CP CU1 provides programmable current signals at the

I OUT output and facilitates measuring of the output current and the voltage at

the test object’s terminals. The current range of 10 A, 20 A, 50 A or 100 A is set

by the CPC 100 software (see 2.3 "Configuring CPC 100" on page 22) and the

current range switch on the front panel of CP CU1 is set manually by the user

(see 2.4 "Setting CP CU1" on page 23).

The output current and the voltage at the test object’s terminals connected to the

CP CU1’s V SENSE input are processed by the coupling unit for measuring with

CPC 100. The output current is transformed by a current transformer with the

transmission ratio 100 A : 2.5 A and the secondary transformer winding wired to

the I AC output. The transformed current at the I AC output is measured via the

CPC 100 CP CU1 Device under test

V1 AC V1 ACI ACI ACI OUT

V SENSEBOOSTEREXT. BOOSTER

CP GB1

(optional)

Dangerous zone


22

I AC input of CPC 100. The test object’s voltage is transformed by a voltage

transformer with the transmission ratio 600 V : 30 V and the secondary

transformer winding wired to the V1 AC output. The transformed voltage at the

V1 AC output is measured via the V1 AC input of CPC 100.

The measurements are performed frequency selective, i.e. only signal

components at the generated frequency different from the mains frequency are

analyzed. Due to the high-power disturbances at the mains frequency, the

spectral components around the mains frequency and its harmonics are filtered

out. For detailed information on the frequency selective measurement, see

"Getting Started with Quick: The frequency selective measurement" in the

CPC 100 Reference Manual.

2.3 Configuring CPC 100

Note: The minimum CPC 100 software version required is V 1.4. If you have an earlier version installed, upgrade the software from the CD-ROM delivered with your CP CU1.

CPC 100 must be configured for CP CU1. To configure CPC 100:

1. Press the Options view selector button.

The Options window with the Device Setup tab selected (see Figure

2-2: "Options Window" below) opens.

Figure 2-2:

Options Window

2. Select CU1 from the External booster combo box.

The CT and VT settings are set according to the built-in current and voltage

transformers automatically.

3. Press the Test Card View view selector button and insert the Quick

(default), Sequencer or Ramping test card. Figure 2-3: "Quick Test Card

Window" below shows the setting using the Quick test card as example.

23

Operation

Figure 2-3:

Quick Test Card

Window

4. Open the item list from the Output Range combo box.

The item list displays the CU1:10A, CU1:20A, CU1:50A and CU1:100A

CP CU1 relevant current ranges.

5. Select VT sel and/or CT sel from the Measured Quantities combo boxes

when measuring with the CP CU1’s built-in voltage and current transformers

to account for their transformation ratio.

6. Select the current range you want to use.

2.4 Setting CP CU1

Set the current range of CP CU1 using the current range switch (see

1.3 "Operating Controls of CP CU1" on page 12) to the value configured by the

CPC 100 software.

Caution: Set the current range switch on the CP CU1’s front panel only when CPC 100 is turned off and the test object is connected to ground with closed grounding switch near the measurement setup.

Note: Current range settings on the test card and on the CP CU1’s front panel must be the same.

Output Range

combo box

Measured

Quantities

combo box


24

25

Applications

3 Applications

3.1 Template Usage

The test procedures running on the measurement setup are controlled by

templates available on the CPC Explorer CD-ROM shipped with your CP CU1

or in the customer area of the OMICRON electronics home page

http://www.omicron.at.

The templates are pairs of XML documents and Microsoft Excel templates

designed by OMICRON electronics for designated applications. The XML

templates are predefined test procedures, often with comments, that run on

CPC 100 and guide the user through the test. Once completed, the XML file is

saved, downloaded to the PC using CPC Explorer and then loaded into the

corresponding Microsoft Excel template. There the results are post processed

and a final test report is generated. The template pairs facilitate and speed

testing with CP CU1 and the evaluation of results.

Note: Some template pairs allow version control. If an error message appears after loading the XML template, use a template pair of the same version.

To run a test procedure according a template:

1. Using CPC Explorer, upload the XML template for the intended application

from the PC to CPC 100.

2. Open the template on CPC 100.

3. Run the test procedure according to the template.

4. After completing the test procedure, save the test in a new file.

5. Using CPC Explorer, download the test results from CPC 100 to your

preferred working directory on the PC.

6. Open the corresponding Microsoft Excel template by double-clicking the

*.xlt file in the folder labeled with the test procedure name.

A Microsoft Excel workbook appears.

7. Click the Load XML-File button and open the *.xml file saved in your

preferred working directory before to load the test results.

8. After all worksheets are filled with data, the test results are calculated.


26

3.2 Safety Instructions for Connecting CP CU1 to

Power Lines

3.2.1 Before Starting

Caution: A lightning discharge to the line under test can cause injury or possibly death of the operating staff. Do not connect the measurement setup to overhead lines if there is a possibility of a thunderstorm over any part of the lines to be measured.

Caution: Connecting the measurement setup to overhead lines with a life parallel system bring about high-voltage hazards. It is strongly recommended to take all parallel lines out of service before proceeding.

Before connecting CP CU1 to overhead lines or power cables (further on

referred to as power lines), you must estimate the open-line voltage as follows.

Follow the instructions below exactly and sequentially to protect yourself from

high-voltage hazards. In addition to the following safety instructions,

observe "Safety Rules" on page 7.

3.2.2 Recommended Current Range Settings

The highest current range allowed by the open-line voltage (see

3.2.4 "Connecting the Measurement Setup to Power Lines" on page 28)

provides the best measurement accuracy. However, depending on the length of

the power line under test, this setting may result in CPC 100 overload due to low

driving voltage. As a rule of thumb, the current range required for the power line

length is given in Table 3-1: "Recommended Current Range Settings" below.

Set the current range switch of CP CU1 to the value according to the table.

Table 3-1:

Recommended Current

Range SettingsLine Impedance Line Length Current

RangeCompliance Voltage

0…1.6 Ω 0…2 km/0…1.5 miles 100 A 50 V

0.8…8 Ω 1…10 km/0.5…5 miles 50 A 100 V

4.0…40 Ω 5…50 km/3…30 miles 20 A 250 V

> 16 Ω > 20 km/15 miles 10 A 500 V

27

Applications

3.2.3 Estimating the Open-Line Voltage

To estimate the open-line voltage:

1. Switch off, short-circuit and ground the power line on both sides using an

installed grounding switch or, if no grounding switch is available on site, using

grounding cables (further on, the grounding switch or these extra grounding

cables are referred to as grounding switch).

2. Make sure that the connection to ground at the far end of the power line is

not removed during the complete test procedure.

3. In addition to the grounding switch, ground the line at the near end using a

grounding set consisting of three cables rated for the maximum short-circuit

current possible on the line. This connection is called working ground further

on.

4. Open the grounding switch at the near end of the power line and measure the

current through the working ground using a clamp-on ammeter on all three

phases.

5. Close the grounding switch.

6. Calculate the estimated open-line voltage after removal of the grounding

cables as follows:

Vest [V] = Imeas [A] × 0.4 [Ω/km] × 2 × lline [km] (Eq. 3-1)

or

Vest [V] = Imeas [A] × 0.64 [Ω/mile] × 2 × lline [miles] (Eq. 3-2)

where Vest [V] is the estimated open-loop voltage in volts,

Imeas is the highest measured current in ampers,

0.4 [Ω/km] = 0.64 [Ω/mile] is the constant of a typical overhead line per wire

and lline [km] and lline [miles] is the length of the line in km and miles respectively.

Caution: If the estimated open-line voltage is

• > 500 V, stop. The measurement is not possible due to high-voltage hazard. Try to take parallel lines out of service.

• 250…500 V, the measurement is possible only in the 10 A range.

• 100…250 V, the measurement is possible in the 10 A or 20 A range.

• 50…100 V, the measurement is possible in the 10 A, 20 A or 50 A range.

• < 50 V, the measurement is possible in all current ranges.

7. If the current range allowed by the estimated open-line-voltage is lower as

the current range set according to Table 3-1: "Recommended Current Range

Settings" on page 26, set the current range switch of CP CU1 to the value

allowed by the open-line voltage.


28

Caution: During the grounding switch at the near end of the power line is open, the area around CP GB1 in the range of 5 m/15 ft and around CP CU1 in the range of 2 m/5 ft is a dangerous zone due to high-voltage and mechanical hazards. Do not enter the dangerous zone. Keep the

grounding switch open for a time as short as possible.

Caution: If you see or hear anything uncommon in the test equipment, e.g. noise of electrical discharge or lightening of surge arrestors, close the grounding switch before touching the measurement setup.

3.2.4 Connecting the Measurement Setup to Power Lines

If the estimated open-line voltage (see 3.2.3 "Estimating the Open-Line Voltage"

on page 27) allows measurement in the current range you want to use, connect

the measurement setup to the power line as follows:

1. Make sure that the grounding switch is closed.

2. Connect CP GB1 to ground using the delivered cable near the place where

the connection to the line is made. Make sure that the grounding stud is in

good condition, clean and free of oxidation.

Caution: Depending on the type of grounding points in the substation, the appropriate connection set and socket clamp have to be used. Connecting socket clamps of one type to a grounding point of another system is highly dangerous on both the connection of the grounding set to CP GB1 and the connection of CP GB1 to the grounding point in the substation. The 16 to 20 mm socket clamps are designed and tested for fault currents up to 26.5 kA, the 25 mm (1 inch) socket clamp for fault currents up to 30 kA, both for a maximum duration of 100 ms. On locations where higher fault currents are possible, CP CU1 and CP GB1 must not be used.

3. Disconnect the grounding cables from the ground (the grounding switch is

closed!) and connect them to the CP GB1’s line studs.

4. Position CP CU1 at a minimum distance of 5 m/15 ft from CP GB1.

5. Position CPC 100 at a minimum distance of 5 m/15 ft from CP CU1 and

10 m/30 ft from CP GB1.

6. Ground CP CU1 using a cable of at least 6 mm2 cross-section close to

CPC 100 and the position of the operator.

7. Connect CP CU1 with CP GB1 as shown in Figure 3-1: "Wiring the

Measurement Setup" on page 29.

29

Applications

Figure 3-1:

Wiring the

Measurement Setup

8. Ground CPC 100 using a cable of at least 6 mm2 cross-section close to the

position of the operator.

9. Connect CP CU1 with CPC 100 as shown in Figure 3-1: "Wiring the

Measurement Setup" above.

10.Mark the area around CP GB1 in the range of at least 5 m/15 ft and around

CP CU1 in the range of at least 2 m/5 ft as dangerous zone.

11.Open the grounding switch and read the voltmeter on the CP CU1’s front

panel from outside of the dangerous zone.

Caution: If the voltmeter’s reading is

• > 500 V, stop. The measurement is not possible due to high-voltage hazard.

• 250…500 V, the measurement is possible only in the 10 A range.

• 100…250 V, the measurement is possible in the 10 A or 20 A range.

• 50…100 V, the measurement is possible in the 10 A, 20 A or 50 A range.

• < 50 V, the measurement is possible in all current ranges.

If the open-line voltage allows measurement, proceed as described in the

respective "Performing Measurements" section of the following applications.

Caution: Make sure that the grounding switch is always closed when no measurement is performed and especially when the wiring is modified or the current range switch of CP CU1 is set.

L3/C L2/B L1/A

Connection using

grounding sets on site


30

3.3 k Factor Measurement

3.3.1 Why k Factor Measurement?

On most modern secondary distance protection relays, the value of the positive-

sequence (line) and zero-sequence (line-to-ground) impedance or the ground

impedance matching factor (k factor) is required to make the relay settings. The

line impedance can be readily calculated but the chosen values for the ground

impedance often do not match the actual conditions. The accuracy of these

settings is crucial to the operation of the relay because they directly affect the

reach of the different protection zones e.g. in case of a line-to-ground fault.

Measurements show that in significant number of cases the k factor of the

measured lines is set more than 20% from its actual value. This can result in

zone under- or overreach and consequently, the selectivity is lost. This situation

is particularly relevant to underground power cables.

The k factors are line parameters independent of the fault location describing the

ratio of the line and ground impedances. The following k factor definitions are

commonly used:

The complex ratio of the ground impedance ZE and the line impedance ZL

kL = ZE/ZL = (Z0/Z1 – 1)/3, (Eq. 3-3)

the complex ratio of the zero-sequence impedance Z0 and the positive-

sequence impedance Z1 (see Figure 3-2: "Zero-Sequence Impedance

Definition" below)

k0 = Z0/Z1 (Eq. 3-4)

and a couple of real values

RE/RL (Eq. 3-5)

XE/XL (Eq. 3-6)

where RE and XE are the real and imaginary parts respectively of the ground

impedance and RL and XL are the real and imaginary parts respectively of the

line impedance.

31

Applications

Figure 3-2:

Zero-Sequence

Impedance Definition

The k factor is an important setting of distance protection relays. The precision

of this setting affects the accuracy of distance protection relays dramatically.

The k factor can be calculated, but the calculation results give only a rough

estimate of the actual value. As a wrong k factor setting can cause worse power

quality, higher risk to lose the system stability and loss of power supply, k factor

measurements are essential for fast, selective and reliable distance protection.

Because there are usually strong disturbances by other lines in service,

measurement at the mains frequency is not feasible. All measurements running

according to the templates are done below and above the mains frequency and

the results are interpolated. From these results the positive- and zero-sequence

impedances as well as the k factor in various formats are calculated.

3.3.2 Performing Measurements

Connect the measurement setup to the overhead lines or power cables under

test following 3.2 "Safety Instructions for Connecting CP CU1 to Power Lines"

on page 26.

Note: For line length below 5 km/3 miles it is recommended to connect the V SENSE input of CP CU1 as close as possible to the VT of the line to reduce the additional impedance of the current feed in the path. For longer lines, you can connect the V SENSE input with the Kelvin clamps directly on CP GB1.


32

In the course of the k factor test procedure, the following measurements are

performed:

• Line-to-line impedance measurements: L1-L2, L1-L3, L2-L3 (Figure

3-3: "Line-to-Line Impedance Measurements" below shows the L1-L2

measurement as example.)

Figure 3-3:

Line-to-Line Impedance

Measurements

CPC 100 CP CU1

CP GB1

Far end Near end

Overhead line

V1 AC V1 ACI ACI AC I OUT


33

Applications

• Line-to-ground impedance measurements: L1-E, L2-E, L3-E (Figure

3-4: "Line-to-Ground Impedance Measurements" below shows the L1-E

measurement as example.)

Figure 3-4:

Line-to-Ground

Impedance

Measurements

CPC 100 CP CU1CP GB1

Far end Near end

Overhead line




34

• Zero-sequence impedance measurements: L1||L2||L3-E (see Figure

3-5: "Zero-Sequence Impedance Measurement" below)

Short the three phases with the delivered three-lead cable as shown in Figure

1-6: "Shorting the Phases" on page 17.

Figure 3-5:

Zero-Sequence

Impedance

Measurement

The test procedure is controlled by templates available on the CPC Explorer

CD-ROM shipped with your CP CU1 or in the customer area of the OMICRON

electronics home page. For detailed information on the templates and

instructions how to use them, see 3.1 "Template Usage" on page 25.

It is recommended to use the same test current for all measurements. To find

out the highest test current possible, start the test procedure with the

measurement featuring the highest impedance, i.e., the L1-L3 measurement on

power cables and the L1-E measurement on overhead lines.

CPC 100 CP CU1

CP GB1

Far end Near end

Overhead line



35

Applications

After wiring the measurement setup to the line under test proceed as follows:

1. Configure CPC 100 as described in 2.3 "Configuring CPC 100" on page 22

for the CP CU1’s current range set by the current range switch.

Caution: The configured current range must not exceed the limit by the open-line voltage.

2. Choose the XML template for the mains frequency

(e.g. "Line Imp CU1 60Hz.xmt" for the 60 Hz mains frequency) and open the

template.

Caution: Open the grounding switch at the near end before making the test and keep it open only during the measurement. Close the grounding switch after the test and before reconnecting the measurement setup.

3. Run the test procedure.

The following measurements are performed:

• Line-to-line measurements: L1-L2, L1-L3, L2-L3

For each measurement, connect the I OUT and V SENSE inputs of

CP CU1 to the corresponding CP GB1’s line studs.

• Line-to-ground-measurements: L1-E, L2-E, L3-E

For each measurement, connect the I OUT and V SENSE inputs of

CP CU1 to the corresponding CP GB1’s line studs.

• Zero-sequence impedance measurement: L1||L2||L3-E

4. If an overload of CPC 100 occurs, reduce the test current or set a lower

current range and run the test procedure once again.

Lower test currents at the two highest frequencies are recommended.

5. Save the test procedure as a file on CPC 100.

6. Download the test file from CPC 100 to the PC using CPC Explorer.

7. Load the test file into the Microsoft Excel template.

The measurement results are displayed.

The measurement of mutual coupling of two power lines is performed in a similar

way. All three phases of both systems under test are connected together and

grounded at the far end of the line. The current II is fed into all the phases of the

system I and the voltage UII is measured on the near end of the system II which

is not grounded here. The mutual coupling factor for the relay II is then given by

kM0 = (UII/II)/ZLII (Eq. 3-7)


36

3.3.3 Interpretation of Measurement Results

To interpret the results of line impedance measurements correctly, you have to

know details about the overhead line or power cable under test. You will find

below some useful notes about how to interpret the measurement results.

Usually, the resistive part of the line impedance is relatively constant over the

L1-L2, L1-L3 and L2-L3 as well as L1-E, L2-E and L3-E measurements. If the

measurement results differ considerably, typically contact problems are the

reason. In some cases, the grounding switches at the far end of the line are not

as good as necessary for the measurement. Additional grounding cables could

help to avoid the contact problems. For the lines under test shorter than

5 km/3 miles, do not connect the V SENSE input of CP CU1 with the Kelvin

clamps, but rather use additional clamps directly on the wires of the power line.

The inductive part of the line impedance increases with the distance between

the lines. This is documented by the measurement results stored in an example

file delivered with the line impedance templates (see the marked results in

Figure 3-6: "Measurement Results" on page 37). The measured overhead line

with the shortest distance between the lines L1 and L3 is shown in Figure

3-7: "Measured Overhead Line" on page 38.

Note: For each line of measurement results there is a separate overload indication top right on the CPC 100’s screen (or in the report) explained below.

No overload indication means no overload during that step of the measurement

sequence.

Dotted overload indication means that there was an overload during that step of

the measurement sequence but not all the time.

Solid overload indication means a permanent overload during that step of the

measurement sequence.

37

Applications

Figure 3-6:

Measurement Results


38

Figure 3-7:

Measured Overhead

Line

The L2-E measurement features the lowest X component because the line is

very close to the ground wire. The X component of the L3-E measurement is

decreased by a parallel system taking course close to L3 on the other side of the

tower. Short-circuiting of the parallel system during the measurement would

have increased the effect and would have lead to erroneous results because this

is not the normal operating condition. The interpretation of the result of zero-

sequence impedance measurement is more difficult. Some methods for

verifying it are shown below.

Several intermediate results are hidden in the Microsoft Excel template due to

their minor importance. However, by clicking on the "+" symbol on the left (see

the lines 32 and 51 in Figure 3-6: "Measurement Results" on page 37) you can

view the individual k factor results for each line. If the individual measurements

are very close to each other and close to the overall k factor, the measurement

is most likely correct. Broadly spread results with the average value close to the

overall k factor value indicate a very asymmetrical line under test but the results

are most likely correct. If the individual k factor measurements differ

considerably from each other, the relay should be set to a value smaller than the

average k factor to avoid zone overreaches.

L2

L1 L3

39

Applications

Another interesting effect can be observed when measuring power cables. If the

screen or shield is very close to the conductors but the conductors are relatively

wide from each other, the inductive part of the line-to-line measurements is

higher than the inductive part of the line-to-ground measurements, resulting in a

negative X component of the calculated impedance ZE. This seemingly strange

result is explained as follows. Recalling (see 3.3.1 "Why k Factor

Measurement?" on page 30) that the zero-sequence impedance is given by

Z0 = Z1 + 3ZE (Eq. 3-8)

and hence

ZE = (Z0 –Z1)/3 (Eq. 3-9)

where Z1 is the positive-sequence impedance and ZE is defined as a difference

between the line-to-ground loop measurement and a half of the line-to-line loop

measurement, the X component of ZE can become negative.

3.4 Ground Impedance and Step Voltage

Measurement

3.4.1 Introduction

A good substation grounding system is crucial to prevent people injury and

damage of equipment. International standards such as

DIN VDE 0101/CENELEC HD637S1, IEEE Std 80-2000 or IEEE Std 81-1983

give guidelines how to measure such impedances.

This application describes the measurement of large substations. Smaller

grounding systems could be tested without connection to an existing overhead

line or power cable and therefore the use of CP CU1 and CP GB1 would not be

necessary. However, the procedure is the same when injecting the current into

a long wire directly from the 6 A AC output. Anyway, when injecting the current

into a test probe, special safety measures are required to avoid hazards when

people approach the test probe.

The current-voltage method as called in CENELEC HD637S1 or fall of potential

method as called in IEEE standards is a good solution to measure the ground

impedance of a substation. Before starting the test procedure, take one

overhead line or power cable leaving the substation under test out of service and

ground it at the far end. Feed a current via this power line into a remote ground.

For larger substations, a distance of the remote ground of at least 5 km/3 miles

is recommended, the minimum distance is 10 times the size of the grounding

system. Then measure the voltages with a test probe at various distances


40

around the substation. If possible, choose the measurement points in a 90º

angle (bird’s-eye view) relative to the current path. In any case, avoid measuring

close (<60º) to the current path.

For an accurate estimate of the step voltage, set the measurement points as

close as 1 m/3 ft to the substation and to each other. The step voltage is

calculated for a certain fault current. Enter the highest possible fault current for

the substation under test in the relevant field of the Microsoft Excel template.

Measurement data at a large distance (typically three times the length of the

substation) from the substation allow the calculation of the overall substation

ground impedance Zground as defined in VDE 0101.


To measure ground impedance and step voltage:

1. Connect the measurement setup to an overhead line or a power cable

leading from the substation under test following 3.2 "Safety Instructions for

Connecting CP CU1 to Power Lines" on page 26.

2. Short the three phases with the delivered three-lead cable as shown in Figure


3. Connect one pin of the CPC 100’s V1 AC input to the ground substation

ground, the other pin to a test probe as shown in Figure 3-8: "Ground

Impedance and Step Voltage Measurement" on page 41.

The V SENSE input and the V1 AC output of CP CU1 are not used in this

application. The voltage is measured directly using the V1 AC input of

CPC 100.

41

Applications

Figure 3-8:

Ground Impedance and

Step Voltage

Measurement




instructions how to use them, see 3.1 "Template Usage" on page 25. Using the

CPC 100’s Sequencer test card, the test procedure runs without user

interaction, performing the recommended six measurements per test probe

position.

Caution: Do not touch the test probe without insulating gloves outside of the substation area. In case of a high-current ground fault within the substation during the test, considerably high voltages could arise in any wire connected to the substation and leading away from it.

90º

CPC 100 CP CU1

CP GB1

V1 AC I ACI AC I OUT

BOOSTEREXT. BOOSTER


42

After wiring the measurement setup to the line proceed as follows:





(e.g. "Ground Imp CU1 60Hz.xmt" for the 60 Hz mains frequency) and open

the template.

3. Select the "Enter Distance Here" card from the template.

4. Select "Save as Default" to reuse this card later on.

5. Stick the test probe into the ground at the specified distance from the

substation and proceed from short to long distances.

Recommended distances for the step voltage measurement are 1 to 15 m in

1 m steps (3 to 45 ft in 3 ft steps) in the first file and 15 to 30 m in 1 m steps

(45 to 90 ft) in the second file. For the ground impedance measurement, 1,

2, 5, 10, 20, 50, 100, 150, 200 m and continuing in 100 m steps (5, 10, 20,

50, 100, 200, 500, 750, 1000 ft and continuing in 250 ft steps) seem to be a

good choice. You can measure the distance for this application conveniently

with a commercial GPS device.

Note: Make sure that the measurement points take course in a 90º angle (bird’s-eye view) relative to the current path and, if possible, avoid additional overhead lines or power cables as well as current paths.

6. Start the test card for the current test point.

7. Label the test card with the distance in units m or ft without blanks, e.g. "10m"

or "30ft".

8. Add one Sequencer test card for every test point you want to measure.

9. Proceed with step 6 as long as you want to measure at another distance.

10.Save the test procedure as a file on CPC 100.

Note: It is recommended to save at most 15 test cards in one file, but having more files is possible.

11.Download the test file(s) from CPC 100 to the PC using CPC Explorer.

12.Load the test file(s) into the Microsoft Excel template.

The ground impedance and the step voltage are displayed as a function of

the distance from the substation.

Note: If there are more files, load one after another.

43

Applications

3.4.3 Interpretation of Measurement Results

Ground Impedance Measurement

Due to the inductance of the feed-in line, a considerable part of the current Iout

injected into the ground does not flow back through the ground but through the

ground wire or the line shield. This current Ishield has to be subtracted from Iout

and, consequently, the ground impedance is given by

Zground = Vmeas/(Iout – Ishield) (Eq. 3-10)

This effect is compensated by the current reduction factor r as defined in the

CENELEC HD637 S :1999. A field in the XML template allows setting the

current reduction factor between 0.01 and 1.00 (1.00 means no current

compensation).

For 110 kV overhead lines, the standard gives typical values of r = 0.98 for steel

ground wires and down to 0.60 for steel/aluminum ground wires. For current

feeding via power cables, the r factor can be as low as 0.01. The effect of the

current Ishield can be eliminated by disconnecting the line shield or the ground

wire of the feed-in line. If the disconnection is not possible, it is recommended to

measure the current Ishield with a clamp-on ammeter and to calculate the current

reduction factor as

r = 1 – Ishield/Iout (Eq. 3-11)

The example file delivered with the templates includes measurement results for

a terrain approaching the optimum. Figure 3-9: "Ground Impedance vs.

Distance for a Terrain Approaching Optimum" on page 44 shows a graph

displayed after loading the example file into the Microsoft Excel template. The

voltage between the grounding system under test and the test probe (and hence

the ground impedance) increases slowly until it reaches an approximately

constant value. This limit value corresponds to the ground impedance Zground,

the impedance of the substation against the "rest of the world". In the example

considered, Zground is approximately 60 mΩ.


44

Figure 3-9:

Ground Impedance vs.

Distance for a Terrain

Approaching Optimum

In some cases, measurement results shows peaks and drops until an area free

of buildings and buried conductors or pipes is reached. Until then, erroneous

results can be obtained. Figure 3-10: "Ground Impedance vs. Distance for a

Difficult Terrain" below shows typical measurement results obtained under such

conditions. The graph shows a peak due to a street lamp close to the test probe.

The street lamp was connected to a protective ground wire approaching the

location of the remote grounding system. Voltage drops can be observed when

the measurement points are set close to objects (i.e. towers of power lines

leaving the substation under test) connected to the grounding system under test.

Figure 3-10:

Ground Impedance vs.

Distance for a Difficult

Terrain

In a difficult terrain, the measurement results may show no noticeable trend until

values converging to a constant are obtained. Consequently, the terrain analysis

on site is of highest importance. Setting the measurement points close to the line

injecting the current results in erroneously high measured values. An area within

the angle of at least 60º relative to the line should be avoided.

45

Applications

Step Voltage Measurement

In opposite to the ground impedance measurement, the measurement of the

step voltage is to be performed in the close vicinity of the grounding system

under test in steps of at most 1 m/3 ft. The highest voltage gradients or step

voltages occur typically at the corners of the grounding system or peripherals

connected to the grounding system, such as the first towers of overhead lines or

similar objects.

The step voltage is given for the fault current set in the Microsoft Excel template.

In some countries it is usual to give the step voltage in V/m per kA of the fault

current. To obtain the step voltage in these units, enter 1 kA in the fault current

field in the Microsoft Excel template and label the graph accordingly.

3.5 Measurement of Coupling into Signal Cables

3.5.1 Introduction

The measurement of the coupling impedance Zk between power and signal lines

is performed for two current loops of the power lines under test. One loop is

shaped by two lines featuring the largest area, the other loop is shaped by three

lines in parallel and the ground. For each loop, the measurement setup is

calibrated by measuring the voltage with the measurement cable short-circuited.


Connect the measurement setup to the overhead lines or power cables under

test following 3.2 "Safety Instructions for Connecting CP CU1 to Power Lines"

on page 26. The V SENSE input and the V1 AC output of CP CU1 are not used

in this application. Position the measurement cable near the connection terminal

of the signal cable.

Note: The voltage is measured directly using the V2 AC input of CPC 100.


46

In the course of the test procedure, the following tests are performed:

• Calibration with the loop shaped by two lines with the largest area (Figure

3-11: "Calibration with the Line-to-Line Loop" below shows the L1-L3

calibration as example)

Short-circuit the measurement cable and connect it to the cable under test.

Figure 3-11:

Calibration with the

Line-to-Line Loop

Short circuitSignal cable

CPC 100 CP CU1

CP GB1


BOOSTEREXT. BOOSTER

47

Applications

• Measurement with the loop shaped by two lines with the largest area (Figure

3-12: "Measurement with the Line-to-Line Loop" below shows the L1-L3

measurement as example)

Figure 3-12:

Measurement with the

Line-to-Line Loop

Signal cable

CPC 100 CP CU1

CP GB1


BOOSTEREXT. BOOSTER


48

• Measurement with the loop shaped by three lines in parallel and the ground

(see Figure 3-13: "Measurement with the Loop Between Parallel Lines and

Ground" below)



Figure 3-13:

Measurement with the

Loop Between Parallel

Lines and Ground

Signal cable

CPC 100 CP CU1

CP GB1


BOOSTEREXT. BOOSTER

49

Applications

• Calibration with the loop shaped by three lines in parallel and the ground (see

Figure 3-14: "Calibration with the Loop Between Parallel Lines and Ground"

below)


1-6: "Shorting the Phases" on page 17. Short-circuit the measurement cable

and connect it to the cable under test.

Figure 3-14:

Calibration with the

Loop Between Parallel

Lines and Ground




instructions how to use them, see 3.1 "Template Usage" on page 25.

Signal cable Short circuit

CPC 100 CP CU1

CP GB1


BOOSTEREXT. BOOSTER


50

After wiring the measurement setup to the line proceed as follows:





(e.g. "Coupling CU1 60Hz.xmt" for the 60 Hz mains frequency) and open the

template.

3. Connect the I OUT output of CP CU1 to the CP GB1’s line studs

corresponding to the line-to-line loop with the largest area (see Figure

3-11: "Calibration with the Line-to-Line Loop" on page 46).

4. Connect a twisted shielded measurement cable to the V2 AC input of

CPC 100 and short-circuit it.

Note: The measurement cable is not part of the scope of supply.

5. Start the "L-L cal" test card.

6. Measure the voltage between the shield of the measurement cable and the

signal cable with a hand-held voltmeter.

Caution: If the measured voltage is

• > 40 V, take safety precautions to avoid electrical hazard.

• > 300 V, stop. The measurement is not possible, because the V2 AC input limits are exceeded.

7. If the voltage allows measurement, connect the measurement cable to the

signal cable (see Figure 3-12: "Measurement with the Line-to-Line Loop" on

page 47).

8. Start the "L-L meas" test card.

9. Connect the I OUT output of CP CU1 to the CP GB1’s line studs

corresponding the loop shaped by three lines in parallel and the ground (see

Figure 3-14: "Calibration with the Loop Between Parallel Lines and Ground"

on page 49).

10.Start the "L-E meas" test card.

11.Disconnect the measurement cable from the signal cable and short-circuit it.

12.Start the "L-E cal" test card.

13.Save the test procedure as a file on CPC 100.

14.Download the test file from CPC 100 to the PC using CPC Explorer.

15.Load the test file into the Microsoft Excel template.

The measurement results are displayed.

51

Technical Data

4 Technical Data

4.1 CP CU1 Output Ranges

Table 4-1:

Output Ranges of

CP CU1

4.2 CP CU1 Measuring Transformers

Table 4-2:

Measuring

Transformers of

CP CU1

4.3 CP CU1 Inputs

Table 4-3:

Inputs of CP CU1

Range Current Compliance Voltage @ > 45 Hz

10 A 0…10 Arms 500 Vrms

20 A 0…20 Arms 250 Vrms

50 A 0…50 Arms 100 Vrms

100 A 0…100 Arms 50 Vrms

Transformer Ratio Accuracy @ 50/60 Hz

VT 600 V : 30 V Class 0.1

CT 100 A : 2.5 A Class 0.1

Characteristic Rating

V SENSEOvervoltage category CAT III (IEC 61010-1)

Voltage range 0…600 Vrms

BOOSTER1

1. The BOOSTER input supplies power to CP CU1. It must be connected only to CPC 100.

Overvoltage category CAT I

Voltage range 0…200 Vrms

Current range 0…30 Arms

Frequency range 15…400 Hz

Fuse 30 A fast acting,

automatic circuit-breaker


52

4.4 CP GB1 Specifications

Table 4-4:

CP GB1 Specifications

4.5 Output Power

Table 4-5:

Output Power of

CPC 100 and CP CU1


Nominal AC spark-over voltage < 1000 Vrms

Impulse spark-over voltage < 2000 Vpeak

Short-circuit proof with:

16 mm cylindrical or 20 mm ball studs 26.5 kA (<100 ms)/67 kApeak

25 mm or 1 inch ball studs 30 kA (<100 ms)/75 kApeak

Torsional moment for changing arrestors > 15 Nm

Characteristic Rating1

1. Ambient temperature 23ºC ± 5ºC/73ºF ± 10ºF

Maximum power

5000 VA (45…70 Hz), cosϕ < 1.0 for 8 s @ 230 V AC

mains voltage

5000 VA (45…70 Hz), cosϕ < 0.4 for 8 s @ 115 V AC

mains voltage

Continuous power 0…1600 VA

Frequency 15…400 Hz (15…45 Hz with reduced voltage)

53

Technical Data

4.6 Accuracy

Table 4-6:

Accuracy of CPC 100

and CP CU1

4.7 Environmental Conditions

Table 4-7:

Environmental

Conditions for CP CU1

and CP GB1

Impedance Range

Typ. Accuracy1

of abs(Z) Value

1. Ambient temperature 23ºC ± 5ºC/73ºF ± 10ºF

Typ. Accuracy1 of Phase Angle

V SENSE Voltage

I OUT Current

Current Range

0.05…0.2 Ω 1.0…0.5% 1.5…0.8º 5…20 V 100 A 100 A

0.2…2 Ω 0.5…0.3% 0.8…0.5º 20…50 V 100…25 A 100 A

2…5 Ω 0.3% 0.5º 100 V 50…20 A 50 A

5…25 Ω 0.3% 0.5º 100…250 V 20…10 A 20 A

25…300 Ω 0.3…1.0% 0.5…1.5º 250…500 V 10…1.5 A 10 A


Operating temperature –10…+55ºC/14…131ºF

Transport & storage temperature –20…+70ºC/–4…158ºF

Relative humidity 5…95%, non-condensing

Safety EN 61010-1

Prepared for IEEE 510, EN 50191 (VDE 0104),

EN 50110-1 (VDE 0105 Part 100),

LAPG 1710.6 NASA "Electrical Safety"

Protection IP20


54

4.8 Mechanical Data

Table 4-8:

Mechanical Data of

CP CU1 and CP GB1

4.9 Clamp-on Ammeter (Accessory)

Specifications

Table 4-9:

Clamp-on Ammeter

Specifications

For detailed information on the clamp-on ammeter, see the Digital Clamp Meter

User’s Manual shipped with the clamp-on ammeter.


CP CU1Dimensions (w × h × d)

450 × 220 × 220 mm/

17.72 × 8.66 × 8.66 inch

Weight 28.5 kg/62.78 lb

CP GB1

Dimensions (Φ × h) 200 × 190 mm/7.87 × 7.48 inch

Weight

4.2 kg/8.81 lb (without grounding cable)

approx. 6.8 kg/13.22 lb

(with grounding cable)


Current AC

Ranges 40 A/400 A with autoranging

Accuracy ±2% @ 50/60 Hz

Resolution 3½ digits

Voltage AC

Range 600 V

Accuracy 1.5% @ 50/500 Hz

Resolution 3½ digits

General

Clamp size 30 mm/1.2 inch

Insulation CAT III/600 V

Battery 2 × LR03

55

Contact Information / Technical Support

Contact Information / Technical

Support

Europe, Africa, Middle East

OMICRON electronics GmbH

Phone: +43 5523 507-333

E-Mail: [email protected]

Web: www.omicron.at

Asia, Pacific

OMICRON electronics Asia Ltd, Hong Kong

Phone: +852 2634 0377


Web: www.omicron.at

North and South America

OMICRON electronics Corp. USA

Phone: +1 713 830-4660 or 1 800 OMICRON


Web: www.omicronusa.com

For addresses of OMICRON offices with customer service centers, regional

sales offices or offices for training, consulting and commissioning please see our

website.

OMICRON Contact Addresses

56

57

Index

Index

Aaddress

manufacturer . . . . . . . . . . . . . . . . . . . . . . 55

arc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

BBOOSTER input . . . . . . . . . . . . . . . . . . . . . . 12

Ccardiac pacemaker . . . . . . . . . . . . . . . . . . . . . 8

CENELEC HD637 S :1999 . . . . . . . . . . . . . . 43

CENELEC HD637S1 . . . . . . . . . . . . . . . . . . 39

clamp-on ammeter . . . . . . . . . . . . . . 20, 27, 43

coupling

into signal cables . . . . . . . . . . . . . . . . . . . 45

mutual . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

coupling impedance . . . . . . . . . . . . . . . . . . . 45

CPC 100 software . . . . . . . . . . . . . . . . . . 21, 23

CPC Explorer . . . . . . . . . . . . . . . . . . . . . . . . 25

CT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

current range switch . . . . . . . . . . . . . . . . . . . 12

current reduction factor . . . . . . . . . . . . . . . . . 43

Ddangerous zone . . . . . . . . . . . . . . . . . . . 28, 29

dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . 54

DIN VDE 0101 . . . . . . . . . . . . . . . . . . . . . . . 39

EEN 50110-1 . . . . . . . . . . . . . . . . . . . . . . . 5, 53

EN 50191 . . . . . . . . . . . . . . . . . . . . . . . . . 5, 53

EN 61010-1 . . . . . . . . . . . . . . . . . . . . . . . . . 53

Ffactor

current reduction . . . . . . . . . . . . . . . . . . . 43

ground impedance matching . . . . . . . . . . 30

k . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30, 38

frequency selective measurements . . . . . . . 22

front panel . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Gground impedance matching factor . . . . . . . 30

grounding cables . . . . . . . . . . . . . . . . . . . . . 27

grounding stud . . . . . . . . . . . . . . . . . . . . 14, 28

grounding switch . . . . . . . . . . . . . . . . . . . . . 27

Hhotline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

II AC output . . . . . . . . . . . . . . . . . . . . . . . . . . 12

I OUT current output . . . . . . . . . . . . . . . . . . 12

IEEE Std 80-2000 . . . . . . . . . . . . . . . . . . . . 39

IEEE Std 81-1983 . . . . . . . . . . . . . . . . . . . . 39

IEEE 510 . . . . . . . . . . . . . . . . . . . . . . . . . 5, 53

impedance

ground . . . . . . . . . . . . . . . 30, 39, 40, 42, 43

line . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36


58

positive-sequence . . . . . . . . . . . . . . . 30, 39

zero-sequence . . . . . . . . . . . . . . . . . . . . . 30

IP20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

Kk factor . . . . . . . . . . . . . . . . . . . . . . . . . . 30, 38

LLAPG 1710.6 NASA . . . . . . . . . . . . . . . . . 5, 53

Mmanufacturer address . . . . . . . . . . . . . . . . . . 55

measurement setup . . . . . . . . . . . . . . . . . . . 21

mutual coupling . . . . . . . . . . . . . . . . . . . . . . . 35

OOMICRON address . . . . . . . . . . . . . . . . . . . . 55

open-line voltage

estimated . . . . . . . . . . . . . . . . . . . . . . . . . 27

measured . . . . . . . . . . . . . . . . . . . . . . . . . 29

operator qualifications . . . . . . . . . . . . . . . . . . . 5

orderly measures . . . . . . . . . . . . . . . . . . . . . . 9

Pparallel

lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

system . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Ssafety instructions . . . . . . . . . . . . . . . . . . . . 26

safety regulations . . . . . . . . . . . . . . . . . . . . . . 5

safety rules . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Service

OMICRON address . . . . . . . . . . . . . . . . . 55

short-circuit bar . . . . . . . . . . . . . . . . . . . . . . 12

socket clamp . . . . . . . . . . . . . . . . . . . . . 16, 28

step voltage . . . . . . . . . . . . . . . . . . . 40, 42, 45

support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

surge arrestor . . . . . . . . . . . . . . . . . . . . . . . . 14

changing . . . . . . . . . . . . . . . . . . . . . . . . . 18

Ttechnical support . . . . . . . . . . . . . . . . . . . . . 55

templates . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

thunderstorm . . . . . . . . . . . . . . . . . . . . . . . . 26

VV SENSE input . . . . . . . . . . . . . . . . . . . . . . . 12

V1 AC output . . . . . . . . . . . . . . . . . . . . . . . . 12

VDE 0101 . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

VDE 0104 . . . . . . . . . . . . . . . . . . . . . . . . . 5, 53

VDE 0105 Part 100 . . . . . . . . . . . . . . . . . 5, 53

voltmeter . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

VT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12, 31

Wweight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

wiring

CP GP1 . . . . . . . . . . . . . . . . . . . . . . . . . . 29

working ground . . . . . . . . . . . . . . . . . . . . . . . 27