Switchgear

Electrical switchgear is an essential component in the electrical power system, responsible for controlling, protecting, and isolating electrical equipment. It is used to de-energize equipment to allow work to be done and to clear faults downstream. Here is a technical description of switchgear, including its types, applications, and categories.

Low voltage Transformer
40.5kV Switchgear
Low voltage Transformer
480V Switchboard

Definition and Purpose

Electrical Switchgear refers to a centralized collection of circuit breakers, fuses, and switches (circuit protection devices) that function to protect, control, and isolate electrical equipment. The main functions of switchgear are:

Protection:
Detects abnormal conditions and disconnects the affected part to prevent damage.

Control:
Manages the distribution of electrical power across various loads.

Isolation:
Ensures that sections of a power system can be de-energized for maintenance or repair without affecting the rest of the system.

Switchgear Test Procedure

Types of Switchgear

Low Voltage Switchgear

Voltage Level:
Up to 1 kV.

Components:
Circuit breakers, busbars, switches, fuses, and protection relays.

Applications:
Used in residential, commercial, and industrial installations for local power distribution.

Siemens 480V Switchboard
Medium Voltage Switchgear

Voltage Level:
1 kV to 36 kV.

Components:
Vacuum circuit breakers, air-insulated switchgear (AIS), gas-insulated switchgear (GIS).

Applications:
Used in utility substations, industrial plants, and commercial buildings to control and protect medium-voltage power distribution.

Example:
Switchgear equipped with vacuum circuit breakers for industrial substations.

Eaton 12kV Switchgear
Medium Voltage Switchgear

Voltage Level:
Above 36 kV.

Components:
Circuit breakers (including SF6 circuit breakers), disconnectors, instrument transformers, protective relays.

Applications:
Primarily used in power transmission networks, electrical substations, and large industrial plants.

Example:
Gas-insulated switchgear (GIS) used in high voltage substations.

Siemens 38kV Arc-Resistant, Gas-Insulated Switchgear

Switchgear Test Procedures

Visual and Mechanical Inspection:
  1. Verify the unit is clean and all shipping bracing, loose parts, and documentation shipped inside cubicles have been removed.
  2. Inspect physical and mechanical condition.
  3. Inspect anchorage, alignment, grounding, and required area clearances.
  4. Inspect insulators for evidence of physical damage or contaminated surfaces.
  5. Exercise all active components.
  6. Verify correct installation and operation.
    7. low voltage switchgear barrier
    low voltage switchgear barrier
  7. Verify appropriate lubrication on moving current-carrying parts and on moving and sliding surfaces.
  8. Verify operation and sequencing of interlocking systems.
  9. Verify that wiring connections are tight and that wiring is secure to prevent damage during routine operation of moving parts.
  10. Inspect mechanical indicating devices for correct operation.
  11. Perform visual and mechanical inspection of surge arresters
  12. Verify that filters are in place and vents are clear.
Perform visual and mechanical inspection of Instrument Transformers (CTs, VTs)
Perform visual and mechanical Control Power Transformers (CPT)
  1. Inspect for physical damage, cracked insulation, broken leads, tightness of connections, defective wiring, and overall general condition.
  2. Verify that primary and secondary fuse or circuit breaker ratings match drawings.
  3. Verify correct functioning of drawout disconnecting contacts, grounding contacts, and interlocks.
Electrical Tests :
  1. Perform insulation-resistance tests on each bus section, phase-to-phase and phase-to-ground, for one minute in accordance with
    2. NETA Table 100.1
  2. Perform a on each bus section, each phase-to-ground with phases not under test grounded, in accordance with manufacturer’s published data. If manufacturer has no recommendation for this test, it shall be in accordance with The test voltage shall be applied for one minute.
    3. NETA Table 100.2
  3. Perform insulation-resistance tests on control wiring with respect to ground. Applied potential shall be 500 volts dc for 300-volt rated cable and 1000 volts dc for 600-volt rated cable. Test duration shall be one minute. For units with solid-state components or control devices that can not tolerate the applied voltage, follow the manufacturer’s recommendation. (optional)
  4. Perform electrical tests on instrument transformers
  5. Perform ground-resistance tests
  6. Test
    7. Metering
  7. Control Power Transformers
    1. Perform insulation-resistance tests. Perform measurements from winding-to-winding and each winding-to-ground. Test voltages shall be in accordance with Table 100.1 unless otherwise specified by the manufacturer.
    2. Perform a turns-ratio test on all tap positions
    3. Perform secondary wiring integrity test. Disconnect transformer at secondary terminals and connect secondary wiring to a rated secondary voltage source. Verify correct potential at all devices.
    4. Verify correct secondary voltage by energizing the primary winding with system voltage. Measure secondary voltage with the secondary wiring disconnected.
    5. Verify correct function of control transfer relays located in the switchgear with multiple control power sources.
  8. Voltage Transformers
    1. Perform secondary wiring integrity test. Verify correct potential at all devices.
    2. Verify secondary voltages by energizing the primary winding with system voltage.
  9. Perform current-injection tests on the entire current circuit in each section of switchgear.
    1. Perform current tests by secondary injection with magnitudes such that a minimum current of 1.0 ampere flows in the secondary circuit. Verify correct magnitude of current at each device in the circuit.
    2. Perform current tests by primary injection with magnitudes such that a minimum of 1.0 ampere flows in the secondary circuit. Verify correct magnitude of current at each device in the circuit. (optional)
  10. Perform system function tests in accordance with ANSI/NETA ECS.
  11. Verify operation of cubicle switchgear/switchboard
    12. Heater
  12. Perform phasing checks on double-ended or dual-source switchgear to insure correct bus phasing from each source.
  13. Perform electrical tests of surge arresters.
NETA Test Procedure

NETA ATS-2017

Switchgear and Switchboard Assemblies

A. Visual and Mechanical Inspection:
  1. Compare equipment nameplate data with drawings and specifications.
  2. Inspect physical and mechanical condition.
  3. Inspect anchorage, alignment, grounding, and required area clearances.
  4. Verify the unit is clean and all shipping bracing, loose parts, and documentation shipped inside cubicles have been removed.
  5. Verify that fuse and circuit breaker sizes and types correspond to drawings and coordination study as well as to the circuit breaker’s address for microprocessor-communication packages.
  6. Verify that current and voltage transformer ratios correspond to drawings.
  7. Verify that wiring connections are tight and that wiring is secure to prevent damage during routine operation of moving parts.
  8. Inspect bolted electrical connections for high resistance using one or more of the following methods:
    1. Use of a low-resistance ohmmeter.
    2. Verify tightness of accessible bolted electrical connections by calibrated torque-wrench method in accordance with manufacturer’s published data or Table 100.12.
    3. Perform Perform thermographic survey. (optional).
  9. Verify operation and sequencing of interlocking systems.
  10. Verify appropriate lubrication on moving current-carrying parts and on moving and sliding surfaces.
  11. Inspect insulators for evidence of physical damage or contaminated surfaces.
  12. Verify correct barrier and shutter installation and operation.
  13. Exercise all active components.
  14. Inspect mechanical indicating devices for correct operation.
  15. Verify that filters are in place and vents are clear.
  16. Perform visual and mechanical inspection of instrument transformers
  17. Perform visual and mechanical inspection of surge arresters
  18. Inspect control power transformers.
    1. Inspect for physical damage, cracked insulation, broken leads, tightness of connections, defective wiring, and overall general condition.
    2. Verify that primary and secondary fuse or circuit breaker ratings match drawings.
    3. Verify correct functioning of drawout disconnecting contacts, grounding contacts, and interlocks.
B. Electrical Tests:
  1. Perform resistance measurements through bolted connections with a low-resistance ohmmeter,
  2. Perform insulation-resistance tests on each bus section, phase-to-phase and phase-to-ground, for one minute in accordance with Table 100.1.
  3. Perform a dielectric withstand voltage test on each bus section, each phase-to-ground with phases not under test grounded, in accordance with manufacturer’s published data. If manufacturer has no recommendation for this test, it shall be in accordance with Table 100.2. The test voltage shall be applied for one minute.
  4. Perform insulation-resistance tests on control wiring with respect to ground. Applied potential shall be 500 volts dc for 300-volt rated cable and 1000 volts dc for 600-volt rated cable. Test duration shall be one minute. For units with solid-state components or control devices that can not tolerate the applied voltage, follow the manufacturer’s recommendation. (optional)
  5. Perform electrical tests on instrument transformers
  6. Perform ground-resistance tests
  7. Test metering devices
  8. Control Power Transformers
    1. Perform insulation-resistance tests. Perform measurements from winding-to-winding and each winding-to-ground. Test voltages shall be in accordance with Table 100.1 unless otherwise specified by the manufacturer.
    2. Perform a turns-ratio test on all tap positions
    3. Perform secondary wiring integrity test. Disconnect transformer at secondary terminals and connect secondary wiring to a rated secondary voltage source. Verify correct potential at all devices.
    4. Verify correct secondary voltage by energizing the primary winding with system voltage. Measure secondary voltage with the secondary wiring disconnected.
    5. Verify correct function of control transfer relays located in the switchgear with multiple control power sources.
  9. Voltage Transformers
    1. Perform secondary wiring integrity test. Verify correct potential at all devices.
    2. Verify secondary voltages by energizing the primary winding with system voltage.
  10. Perform current-injection tests on the entire current circuit in each section of switchgear.
    1. Perform current tests by secondary injection with magnitudes such that a minimum current of 1.0 ampere flows in the secondary circuit. Verify correct magnitude of current at each device in the circuit.
    2. Perform current tests by primary injection with magnitudes such that a minimum of 1.0 ampere flows in the secondary circuit. Verify correct magnitude of current at each device in the circuit. (optional)
  11. Perform system function tests in accordance with ANSI/NETA ECS.
  12. Verify operation of cubicle switchgear/switchboard space heaters.
  13. Perform phasing checks on double-ended or dual-source switchgear to insure correct bus phasing from each source.
  14. Perform electrical tests of surge arresters.
C. Test Values – Visual and Mechanical
  1. Compare bolted connection resistance values to values of similar connections. Investigate values which deviate from those of similar bolted connections by more than 50 percent of the lowest value.
  2. Bolt-torque levels shall be in accordance with manufacturer’s published data. In the absence of manufacturer’s published data, use Table 100.12.
  3. Results of the Perform thermographic survey shall be in accordance with Section 9. (optional)
D. Test Values – Electrical
  1. Compare bolted connection resistance values to values of similar connections. Investigate values which deviate from those of similar bolted connections by more than 50 percent of the lowest value.
  2. Insulation-resistance values of bus insulation shall be in accordance with manufacturer’s published data. In the absence of manufacturer’s published data, use Table 100.1. Values of insulation resistance less than this table or manufacturer’s recommendations should be investigated. Dielectric withstand voltage tests shall not proceed until insulation-resistance levels are raised above minimum values.
  3. If no evidence of distress or insulation failure is observed by the end of the total time of voltage application during the dielectric withstand test, the test specimen is considered to have passed the test.
  4. Minimum insulation-resistance values of control wiring shall not be less than two megohms.
  5. Results of electrical tests on instrument transformers shall be in accordance with Section 7.10.
  6. Results of ground-resistance tests shall be in accordance with Section 7.13.
  7. Accuracy of metering devices shall be in accordance with Section 7.11.
  8. Control Power Transformers
    1. Insulation-resistance values of control power transformers shall be in accordance with manufacturer’s published data. In the absence of manufacturer’s published data, use Table 100.1. Values of insulation resistance less than this table or manufacturer’s recommendations should be investigated.
    2. Turns-ratio test results shall not deviate by more than one-half percent from either the adjacent coils or the calculated ratio.
    3. Secondary wiring shall be in accordance with design drawings and specifications.
    4. Secondary voltage shall be in accordance with design specifications.
    5. Control transfer relays shall perform as designed.
    6. Voltage transformers
    1. Secondary wiring shall be in accordance with design drawings and specifications.
    2. Secondary voltage shall be in accordance with design specifications
  9. Current-injection tests shall prove current wiring is in accordance with design specifications.
  10. Results of system function tests shall be in accordance with ANSI/NETA ECS.
  11. Heaters shall be operational.
  12. Phasing checks shall prove the switchgear or switchboard phasing is correct and in accordance with the system design.
  13. Results of electrical tests on surge arresters shall be in accordance with Section 7.19.

NETA MTS-2019

7.1 Switchgear, Switchboard, and Panelboard

A. Visual and Mechanical Inspection:
  1. Inspect physical, electrical, and mechanical condition.
  2. Inspect anchorage, alignment, grounding, and required area clearances.
  3. Prior to cleaning the unit, perform as-found tests, if required
  4. Clean the unit.
  5. Verify that fuse and/or circuit breaker sizes and types correspond to drawings and coordination study as well as to the circuit breaker address for microprocessorcommunication packages.
  6. Verify that current and voltage transformer ratios correspond to drawings.
  7. Verify that wiring connections are tight and that wiring is secure to prevent damage during routine operation of moving parts.
  8. Inspect bolted electrical connections for high resistance using one or more of the following methods:
    1. Use of a low-resistance ohmmeter.
    2. Verify tightness of accessible bolted electrical connections by calibrated torque-wrench method in accordance with manufacturer’s published data or Table 100.12.
    3. Perform Perform thermographic survey. (optional).
  9. Confirm correct operation and sequencing of electrical and mechanical interlock systems.
    1. Attempt closure on locked-open devices. Attempt to open locked-closed devices.
    2. Make key exchange with all devices included in the interlock scheme as applicable.
  10. Use appropriate lubrication on moving current-carrying parts and on moving and sliding surfaces.
  11. Inspect insulators for evidence of physical damage or contaminated surfaces.
  12. Verify correct barrier and shutter installation and operation.
  13. Exercise all active components.
  14. Inspect mechanical indicating devices for correct operation.
  15. Verify that filters are in place and/or vents are clear.
  16. Perform visual and mechanical inspection of instrument transformers
  17. Perform visual and mechanical inspection of surge arresters
  18. Inspect control power transformers.
    1. Inspect for physical damage, cracked insulation, broken leads, tightness of connections, defective wiring, and overall general condition.
    2. Verify that primary and secondary fuse ratings or circuit breakers match drawings.
    3. Verify correct functioning of drawout disconnecting and grounding contacts and interlocks.
  19. Perform as-left tests.
B. Electrical Tests:
  1. Perform resistance measurements through bolted electrical connections with a lowresistance ohmmeter
  2. Perform insulation-resistance tests for one minute on each bus section, phase-to-phase and phase-to-ground. Apply voltage in accordance with manufacturer’s published data. In the absence of manufacturer’s published data, use Table 100.1.
  3. Perform a dielectric withstand voltage test on each bus section, each phase-to-ground with phases not under test grounded, in accordance with manufacturer’s published data. within the absence of manufacturer’s published data, use Table 100.2. The test voltage shall be applied for one minute. Refer to Section 7.1.3 before performing test. (optional)
  4. Perform insulation-resistance tests on control wiring with respect to ground. The applied potential shall be 500 volts dc for 300-volt rated cable and 1000 volts dc for 600-volt rated cable. Test duration shall be one minute. For units with solid-state components or control devices that cannot tolerate the applied voltage, follow manufacturer’s recommendation. (optional)
  5. Perform electrical tests on instrument transformers in accordance with Section 7.10.
  6. Perform ground-resistance tests in accordance with Section 7.13.
  7. Test metering devices in accordance with Section 7.11.
  8. Control Power Transformers.
    1. Perform insulation-resistance tests. Perform measurements from winding-to-winding and each winding-to-ground. Test voltages shall be in accordance with manufacturer’s published data. In the absence of manufacturer’s published data, use Table 100.1.
    2. Verify correct function of control transfer relays located in switchgear with multiple power sources.
  9. Verify operation of switchgear/switchboard heaters and their controller.
  10. Perform electrical tests of surge arresters.
  11. Perform online partial-discharge survey in accordance with Section 11. (optional)
  12. Perform system function tests
C. Test Values – Visual and Mechanical
  1. Compare bolted connection resistance values to values of similar connections. Investigate values which deviate from those of similar bolted connections by more than 50 percent of the lowest value.
  2. Bolt-torque levels should be in accordance with manufacturer’s published data. In the absence of manufacturer’s published data, use Table 100.12.
  3. Results of the Perform thermographic survey shall be in accordance with Section 9. (optional)
D. Test Values – Electrical
  1. Compare bolted connection resistance values to values of similar connections. Investigate values which deviate from those of similar bolted connections by more than 50 percent of the lowest value.
  2. Insulation-resistance values of bus insulation should be in accordance with manufacturer’s published data. In the absence of manufacturer’s published data, use Table 100.1. Values of insulation resistance less than this table or manufacturer’s recommendations should be investigated. Dielectric withstand voltage tests should not proceed until insulation-resistance levels are raised above minimum values.
  3. If no evidence of distress or insulation failure is observed by the end of the total time of voltage application during the test, the test dielectric withstand voltage specimen is considered to have passed the test.
  4. Minimum insulation-resistance values of control wiring should be comparable to previously obtained results but not less than two megohms.
  5. Results of electrical tests on instrument transformers should be in accordance with Section 7.10.
  6. Results of ground resistance tests should be in accordance with Section 7.13.
  7. Accuracy of metering devices should be in accordance with Section 7.11.
  8. Control Power Transformers
  9. Heaters should be operational.
  10. Results of electrical tests on surge arresters shall be in accordance with Section 7.19.
  11. Results of online partial-discharge survey should be in accordance with manufacturer’s published data. In the absence of manufacturer’s published data, refer to Table 100.23.
  12. Results of system function tests shall be in accordance with Section 8.
Neta Table 100.5
Neta Table 100.2
Neta Table 100.5
Neta Table 100.5