Underground Cable Testing: High and Low Voltage

CONTENTS PAGE
1 INTRODUCTION ............................................................................................. 4
2 TOOLS AND EQUIPMENT ................................................................................. 4
3 TRAINING ... 4
3.1 Training, Assessment and Authorisation ........................................................... 4
4 PRELIMINARY CHECKS ................................................................................... 4
4.1 Visual Check ................................................................................................. 4
4.2 Notification ................................................................................................... 4
4.3 Worksite Hazard Identification, Risk Assessment and Control (worksite HIRAC) ..... 4
5 METHOD ... 5
5.1 High Voltage Cable Tests ................................................................................ 5
5.2 Insulated Resistance Test – Level 1 .................................................................. 5
5.3 High Voltage Test – Level 2 (Paper Lead Cables Only) ........................................ 6
5.4 Delayed Connection to Network ....................................................................... 6
5.5 Low Voltage Cable Test .................................................................................. 7
5.6 Continuity – Test 1 ........................................................................................ 7
5.7 Serving Insulation Resistance – Test 2 ............................................................. 8
5.8 Insulation Resistance – Test 3 ......................................................................... 8
5.9 Method – Streetlighting Cable Tests ................................................................. 8
5.9.1 Polarity Test ............................................................................................. 8
5.10 Failure to Comply .......................................................................................... 9
6 RECORDS ... 9
7 KEY TERMS AND DEFINITIONS ........................................................................ 9
8 REFERENCES ................................................................................................ 10
9 REVISIONS .................................................................................................. 10


1 INTRODUCTION

This document proves the high and low voltage cable integrity after installation or jointing work is completed and before connection or reconnection to the Essential Energy‟s Network. Such testing and commissioning will be undertaken by people, who are both qualified and authorised, and the relevant test results will be duly entered into the relevant test report form (refer to CEOF6022 and CEOF6023). This document is intended for use by Essential Energy‟s Accredited Service Providers and internal staff for testing of cables before being energised.

2 TOOLS AND EQUIPMENT

Danger HV Test Signs 1000V DC Megger
Insulating Gloves 500V DC Megger
Insulated Ground Matting Low Voltage Tester
Suitable HV Test Equipment Foster Test Set (For paper cable only)

3 TRAINING
3.1 Training, Assessment and Authorisation

Where there is exposure to risk from electrical apparatus a person undertaking work will be appropriately qualified, trained and assessed as competent and authorised to carry out the work.

4 PRELIMINARY CHECKS
4.1 Visual Check

A visual check is carried out by the Authorised Person to ensure that the workmanship of both the installation of the cable and cable jointing work meets Essential Energy‟s requirements before being connected to the Network.

4.2 Notification

The Quality Control Coordinator will be notified 3 working days prior to the commencement of the cable tests. The Accredited Service Provider will be responsible for ensuring that the completed work is tested and test reports are forwarded to the Quality Control Coordinator promptly. The Quality Control Coordinator may be present to witness the testing procedure.

4.3 Worksite Hazard Identification, Risk Assessment and Control (worksite HIRAC)

Tests on underground cables are potentially hazardous to both personnel undertaking the test and the general public in the vicinity. A Worksite HIRAC will be carried out, by the Authorised Person, which will determine the precautions that need to be adopted. For public areas warning signs may need to be displayed and barricades erected around the test area (including all exposed cable terminations) prior to commencing any testing activity.

For HV and LV cable Insulation Resistance tests, a Test Access Permit is not mandatory if the Insulation Resistance test is performed at a 1000 volts DC or less and the cable is discharged to earth for a time duration equal to the test time. If an Access Permit for Testing is deemed necessary after a HIRAC evaluation it will be completed and issued in accordance with CEOP2045 Access Permits. If currently on a ,,Work‟ Access Permit, remove earths and cancel the Access Permit

If the cable has previously been commissioned and connected to Essential Energy‟s System call System Operations and inform them if you require a Test Access Permit to test a high voltage cable, and at all times give full details of location, open points etc

Insulating gloves and ground matting to be utilised.

5 METHOD
5.1 High Voltage Cable Tests

Authorised Persons will complete the prescribed tests as specified. All cables must be fully discharged for a time duration equal to the test time upon completion of each test by means of discharge function on test equipment or an independent earth.
Test results will be recorded on the HV Underground Cable Test Report form, refer to CEOF6022.

5.2 Insulated Resistance Test – Level 1

Screen to Earth Test for XLPE insulated cables will record an insulation resistance as per table below at 500V after one (1) minute. This test will be performed first so as to assist in the reconnection process of the screen to earth connection Phase to Screen/Earth, and Phase to Phase testing requires the Authorised Person to measure insulation resistance at 1.kV after one (1) minute duration. Minimum IR as per table below.


5.3 High Voltage Test – Level 2 (Paper Lead Cables Only)

If the insulation resistance results for Paper Lead (PLY) cables are below the prescribed minimum values, a high voltage DC test will be applied. See CEOF6022 HV Underground cable Test Report for the prescribed minimum values. If prescribed minimum values are required for higher voltage Paper Lead (PLY) cables, contact Quality Control Coordinator. It is performed by applying a DC voltage between phases and between phases and sheath. When making these tests, the voltage will be increased gradually to the full specified value and be maintained for 15 minutes. After 15 minutes, the leakage current should be steady or falling and less then 0.1mA with no transient spikes occurring. Higher readings may be acceptable provided they are steady. For further advice, contact Quality Control Coordinator Commissioning new cables – a cable not previously energised will be tested by applying:

11kV cable
34kV DC between phases; and
68 kV DC between phases; and

22kV cable
25kV DC between phases and sheaths
50 kV DC between phases and sheath


The 3 phases can be bonded for the phase to sheath test and only 1 test made unless a failure occurs. If a failure occurs, each phase will be tested individually to determine the faulty phase.
Recommissioning Existing Cables – where a cable that has been in service, is to be tested prior to recommissioning, it will be tested at approximately 75% of the voltages for a new cable, i.e.

11kV cable
26kV DC between phases; and
52kV DC between phases; and
22kV cable
15kV DC between phases and sheath
30kV DC between phases and sheath

The phases can be bonded for the phase to sheath test, and only one test made unless a failure occurs.

5.4 Delayed Connection to Network
Insulation Integrity Test

If a cable is to be connected to the Network and the testing has occurred within 4 weeks preceding this, a visual inspection of the cable location will be undertaken, for any obvious signs that cable insulation integrity may have been compromised. After 4 weeks has elapsed the standard test must be repeated before connection is carried out. This time frame also applies to cables which have been removed from service for repair or have been decommissioned.
If live line techniques are to be utilised for cable connection a documented cable test must be carried out (CEOF6022 HV Underground Cable Test Report) to determine the insulation integrity of the cable prior to carrying out live line technique.

If an Insulation Integrity test is to be undertaken the live line gang must inform System Operations of the insulation integrity test before the live line work is carried out. Once the integrity of the insulation is proven, inform System Operations of the result (if the cable fails the test, commissioning of the cable will not proceed any further and Quality Control Coordinator will be contacted for further advice).
Live Line work will be carried out as per switching sheet.
The Standard Tests, Phase to Phase and Phase to earth:
Measure insulation resistance at 1kV after one (1) minute.
Acceptable values for existing cables may be used as cable will now be connected to switchgear etc.



All cables must be fully discharged for a time duration equal to the test time upon completion of each test by means of discharge function on test equipment or an independent earth.
The purpose of this test is to prove that the integrity of the insulation has not been damaged since the original test date.
The energising/de-energising of an underground cable which is to be directly connected to the overhead system and is isolated from the transformer must only be undertaken using a temporary EDO (cut-out tool) fitted with a 25 amp K class fuse element.

5.5 Low Voltage Cable Test

Authorised Persons will complete the prescribed tests as specified. All cables must be fully discharged for a time, duration equal to the test time upon completion of each test by means of the discharge function on test equipment or an independent earth. Test results will be recorded on CEOF6023 LV Underground Cable Test Report form.

5.6 Continuity – Test 1

The continuity test (DC resistance measurement) will be carried out on each low voltage circuit from the end of each branch or open point, to the origin of the circuit.

Step 1 At the circuit origin, to be tested, (normally at the Padmount transformer), connect each of the phase conductors to the neutral of the cable circuit in turn, ensuring all MEN points are disconnected.
Step 2 At the remote ends of the circuit, check for continuity between each phase and neutral.
Results very close to a short circuit value should be obtained.
Step 3 At the circuit origin (normally at the Padmount transformer) connect the phase conductors together, remaining separate from neutral conductor.
Alternatively, if cable is to be energised immediately after testing, neutral polarity may be tested by ,,lamping out‟ conductors at each pit or pillar.
Step 4 Proceed to each pit or pillar on the circuit and check neutral polarity with 500V megger. If any reading other than an open circuit is recorded between the connected phases and neutral, it will mean a phase has been connected to the neutral which will be located, rectified and retested before connection to Essential Energy‟s Distribution System.

5.7 Serving Insulation Resistance – Test 2

The integrity of the covering sheath will be proved by bonding the 4 cores and applying 500V DC for 1 minute between the bonded cores and earth. The minimum insulation resistance will be 200 Megohms for new cables and 20 Megohms for cables older than 1 year.
If the cables fail this test, the point of failure will be located, rectified and retested before connection to Essential Energy‟s Distribution System.

5.8 Insulation Resistance – Test 3

Ensuring all cores are separated from each other and using a 500V instrument measure the insulation resistance between 2 cores in rotation, i.e.: N-R, R-W, N-W, R-B, N-B, B-W.
The minimum insulation resistance will be 200 Megohms for new cables and 20 Megohms for cables older than 1 year.
If a cable fails to achieve the required minimum values, contact Quality Control Coordinator or the Principal‟s Superintendent for further advice.
Ensure all MEN points have been reconnected.

5.9 Method – Streetlighting Cable Tests
5.9.1 Polarity Test

CHECK all connections in the service pit/pillar and ensure they are correct ENSURE primary fuse is removed or circuit breaker is switched off, incoming neutral isolated, earths disconnected, PE cell and tubes/globes removed CONFIRM visually the colour coding of internal wiring at terminal block is correct. Ensure terminal block is not earthed at light fitting USING 500V megger measure insulation resistance between internal wiring and standard (reading to exceed 1 megohm), test for short circuits and reconnect earth if applicable TEST and identify streetlight active and neutral. Connect service neutral to streetlight neutral first, then service active to streetlight active CHECK all connections in the street light column and ensure they are correct INSERT PE cell, tube/globe, fuse or circuit breaker. Ensure streetlight operates CONDUCT "final test" with streetlight on measuring between an independent earth and neutral and earth or metal work for any voltage.

5.10 Failure to Comply

If a cable or associated equipment fail a prescribed test, the Accredited Service Provider will be responsible for the location of the fault, repair or replacement of faulty cable and/or accessories, and any subsequent testing, as directed by Quality Control Coordinator.
Prior to the application of any fault location methods which have the potential to affect the long-term insulation integrity of the installation, the Authorised Service Provider will submit to Essential Energy a proposed fault location methodology. No fault location work will proceed until Essential Energy‟s Quality Control Coordinator has given approval.

6 RECORDS

The relevant test results will be duly entered on the relevant Test Report form, (See CEOF6022 and CEOF6023.)
The Cable Test Report will be sighted by the person carrying out the commissioning who completes the clearance certification by signing, therefore accepting the new asset.
The person carrying out the commissioning will quote the Cable Test Report No. to System Operations when requesting energisation of new asset. This will be System Operations record of compliance until paper copy is received.
The Quality Control Coordinator is also responsible for correct distribution of Cable Test Report copies.

1 Quality Control Coordinator – WHITE
2 Project File – BLUE
3 System Operations – YELLOW
4 Book copy – PINK.


7 KEY TERMS AND DEFINI KEY

Accredited Service Provider: refers to companies/sole traders who have gained accreditation through the Department of Fair Trading allowing them to perform contestable works.
Authorised Person: means a person with technical knowledge or sufficient experience who has demonstrated competency and has been approved by Essential Energy to carry out specific duties with the supply or use of electricity.
Contestable Works: those works where the customer has a choice of Service Provider.
Continuity test: test to ensure correct cable core identity and continuity.
Essential Energy's Network: Essential Energy Transmission and Distribution System Assets.
Insulation Resistance: quantified measurement of insulation value.
Polarity test: test to ascertain correct identification and connection of active and neutral conductors.
Principal's Superintendent: Project Manager of the Accredited Service Provider.
Quality Control Coordinator: is the person nominated by Essential Energy with the responsibility for auditing construction works to Essential Energy‟s standards and quality.
System Operations: Essential Energy 24 hour Operational Control Centre.


8 REFERENCES

CEOF6022 – HV Underground Cable Test Report
CEOF6023 – LV Underground Cable Test Report
CEOP2018 – Polarity and Neutral Identification Testing
CEOP2045 – Access Permits
CEOP8029 – Network Management Plan
CEOP8030 – Electrical Safety Rules
Olex Cables – Technical Informative PT-I 316 – 24th May 2001
Electricity Supply (Safety and Network Management) Regulation 2002