Module 2 Commissioning Switch Gear Assemblies

04/09/23 Module Two 1

SUBSTATION COMMISSIONING COURSE

MODULE TWO

SWITCHGEAR ASSEMBLIESTESTING PROCEDURES


INTRODUCTION

• The electrical commissioning and acceptance testing of electric power systems is essential for the energization of any electrical system for the first time.


INTRODUCTION

Module Two:• Introduce the NETA acceptance

testing procedures– Visual and mechanical

inspections– Electrical tests– Assessment of test results

• Test equipment operation & hands on testing

• Adopting safe work practices


INTRODUCTION

By the end of MODULE ZERO:• Perform acceptance testing

procedure for switchgear assemblies

• Operate insulation and dielectric test equipment

• Operate Digital Low Resistance Ohmmeter (DLRO)

• Apply safe work practices• Analyze test values• Complete test forms


ELECTRICAL TESTING

• Majority of testing is to check the insulation system integrity

• Types of Solid Insulation testing:– Insulation Resistance test

• Prelude for the Dielectric Withstand– Dielectric Withstand test

• Survivability for high voltage spikes– Switching, lightning induced over

voltages and transients


TESTING

Insulation Testing:• Insulation

Resistance

DC Insulation Resistance Test• Conducted at 100% of

operating stress level• AC RMS voltage x 1.414• Voltage applied < 1000 V/s• Voltage held for 1 minute• If “pass”, proceed to dielectric

withstand test

– NOTE: Voltage level specified is higher than NETA test voltage


TESTING


Resistance

Test Volt. Calculation example:

Nameplate Rated voltage: 5 kV

Ø – gnd voltage = 5 kV / 1.732

= 2.887 kV

Crest Voltage = 2.9 kV x 1.414

= 4.1 kV

Test Voltage = 4.1 kV


ELECTRICAL TESTING


TESTING


Resistance

IR Test Procedure:• Isolate equipment• Prepare the DUT• Prepare the Test set• Apply test voltage


TESTING

Insulation Testing:• Insulation Resistance

Test Procedure– Isolate equipment– Prepare the DUT– Prepare the Test set– Apply test voltage

Isolate Equipment / DUT:• Apply isolation / lock-out /

grounding procedure• Obtain test and work

permit• Install DANGER HIGH

VOLTAGE – TESTING IN PROGRESS warning signs

• Install barrier tape or high visibility rope barrier


TESTING


TESTING



Prepare the DUT:• Disconnect all incoming

and outgoing cables– Maintain adequate

clearance• Remove primary fuses

from VT / PT’s and CPT• Disconnect surge arrestors


TESTING



Prepare the Test Set:• Functional check

– Battery Level– Calibration date– Short circuit test– Recording paper

• Link computer software• Use grounded plug / GFI if

AC powered


TESTING



Apply test voltage:• Apply test voltage• Test to the desired time

interval• Discharge / ground tested

phase before changing / removing connections

• Review test data• Proceed to dielectric test

IF results are satisfactory !


TESTINGNETA Insulation Resistance Test Voltage level


TESTING

Insulation Testing:• Dielectric Withstand

Dielectric Withstand Test• AC / DC depending on class• Factory Test + 200% of rated

voltage• Field acceptance test @ 75% of

Factory level


ELECTRICAL TESTING


AC Dielectric Withstand Test• Rated power frequency, 60 Hz • Voltage applied at a rate

< 1000 V per second• Voltage held for 1 minute

CAUTION: AC Hipot can be a destructive test


ELECTRICAL TESTING


Factory AC Dielectric Withstand Test as per IEEE C37.20.2

Rated max Volts Test Volts

(kV rms) (kV rms)

4.76 14.0

8.25 27.0

15.0 27.0

27.0 38.0

38.0 60.0


ELECTRICAL TESTING

Phase A Hot: AC Hipot, Breaker Connected & Closed


ELECTRICAL TESTING

Phase B Hot: AC Hipot, Breaker Connected & Closed


ELECTRICAL TESTING

Phase C Hot: AC Hipot, Breaker Connected & Closed


ELECTRICAL TESTING

Phase A Hot: AC Hipot, Breaker Connected & Opened


ELECTRICAL TESTING

Phase B Hot: AC Hipot, Breaker Connected & Opened


ELECTRICAL TESTING

Phase C Hot: AC Hipot, Breaker Connected & Opened


TESTING


60 Hz

Dielectric Test Procedure:• Isolate equipment• Prepare the DUT• Prepare the Test set• Apply test voltage


TESTING

Insulation Testing:• Dielectric Withstand Test

Procedure - 60 Hz– Isolate equipment– Prepare the DUT– Prepare the Test set– Apply test voltage







TESTING


TESTING


Procedure – 60 Hz– Isolate equipment– Prepare the DUT– Prepare the Test set– Apply test voltage

Prepare the DUT:• Disconnect all incoming

and outgoing cables– Maintain adequate

clearance• Remove primary fuses

from VT / PT’s and CPT• Disconnect surge arrestors• Ensure equipment is

grounded


TESTING



Prepare the Test Set:• Perform functional check

– Spark Gap test– Recording paper

• Link computer software• Use grounded plug / GFI• Ground test set to

equipment ground


TESTING



Apply test voltage:• Apply test voltage• Test to the desired time

interval• Discharge / ground tested

phase before changing / removing connections

• Review test data


TESTING

Dielectric Withstand Test – 60 Hz• Some manufacturer recommend Low Frequency

withstand voltage VS Power Frequency• Field test voltage levels are the same• Field test voltage at 75% of factory test voltage• DC Hipot is not recommended but not prohibited


TESTING

Dielectric Withstand Test – DC• Will not be presented• Included in the manual for the sake of

completeness


TESTING

Low Resistance test• Measures bolted connection resistance

– Bus bar to bus bar resistance– Bus bars to cable resistance

• DC test at constant 100 ADC or higher• Joints must be torque to specified force (ft-lbs)• Values are compared to similar joints• High reading joints are inspected / retorque /

reassembled and retested


TESTING

Low Resistance test• Access to main bus compartment required

– Remove metal barriers for access– Insulating boots for bolted joints removed

• Measure on a per phase basis• Resistance calculated based on Ohm’s Law

– Example: – 1 mV across joint equates to 10 μΩ– (1 X 10-3 V) / (1 x 102 A) = 1 x 10-5 = 10 x 10-6


TESTING


TESTING

Low Voltage Testing:• Low Resistance

Test Procedure

Low Resistance test:• Isolate equipment• Prepare the DUT• Prepare the Test set• Apply test current


TESTING

Low Test Resistance Procedure– Isolate equipment– Prepare the DUT– Prepare the Test set– Apply test current







TESTING


TESTING


Prepare the DUT:• Ensure equipment is

grounded


TESTING


Prepare the Test Set:• Perform functional check

– Calibration resistor• Use grounded plug / GFI


TESTING


Apply test current:• Apply test current• Measure resistance of all

bolted connections• Measure resistance of all

breaker connections– Sliding contacts– Main contacts

• Review test data


SAFETY AWARENESS & PRACTICE

• HV testing is an electrical shock potential• Test set operators must:

– be aware of the hazards involved in performing the task

– take the required safety precautions and restrict access to anyone not involved in the testing process

– be properly trained in the equipment operations – recognize and avoid the hazards– be trained in safe work practices and procedures


SAFETY AWARENESS & PRACTICEQualified person

A qualified person shall be trained and knowledgeable of the construction and operation of equipment or a specific work method, and be trained to recognize and avoid the electrical hazard that might be present with respect to

that equipment or work method. Such persons shall also be familiar with the proper use of special precautionary techniques, personal protective equipment, insulating and shielding material, and insulating tools and test

equipment.


Qualification of Qualified Person1. Basic understanding of

electricity

2. Working knowledge of test equipment and hazards with the test and equipment

3. Understand approach distances

4. Trained is safe work practices and procedures

5. Understand the factors affecting severity of electrical shock

6. Know the effects of current to the body

7. Trained on releasing a victim from energized circuit

8. Trained not to contact a device under test

9. Understand that enclosure and test equipment must be grounded

10. Know that DUT must be discharge before changing / removing any connections



• Engineering controls and work practices primary factors for safeguarding against risk of injury

• PPE is not an alternative to safe work practices



Resources:• IEEE Standard 510 – 1983,

Recommended Practice for Safety in High Voltage & High Power Testing

• NEMA Standard Publication SG 10 – 2008, Guide to OSHA and NFPA 70E Safety Requirements When Servicing and Maintaining Medium-Voltage Switchgear and Circuit Breakers Rated above 1000 Volts.


NETA STANDARD

3. NETA Acceptance Testing Procedures 3.1 Visual and Mechanical Inspection 3.2 Electrical Test 3.3 Test values analysis 3.3.1 Visual and Mechanical 3.3.2 Electrical


TEST SET MANUALS

15 KV Insulation Resistance Test set

AC High Potential Test set DC High Potential Test set Digital Low Resistance Test set


TEST FORM

Switchgear Inspection Check List Form Bus Resistance Test Form Bus Insulation Test Form

Module 2 Commissioning Switch Gear Assemblies

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