Complete Commissioning Process for 10KV KYN28-12 High-Voltage Switchgear

KYN28-12 is the mainstream model of 10KV mid-mounted high-voltage switchgear. The commissioning core revolves around three key aspects: primary circuit insulation/on-off performance, secondary circuit control/protection, and five-prevention mechanical & electrical interlocking. It follows the process of preliminary preparation → unit commissioning → interlock commissioning → withstand voltage test → protection setting → no-load commissioning run. The safety specifications for high-voltage operations (operation by two or more personnel, on-the-job with valid certificates) must be implemented throughout the entire process.

The following commissioning process is the standard procedure for on-site newly installed switchgear. For renovated/overhauled switchgear, links such as no-load test and cabinet appearance inspection can be omitted on this basis, with the focus on strengthening circuit retesting and interlocking verification.

1. Preliminary Preparation for Commissioning (Safety + Basic Inspection, Top Priority)
2. Personnel and Qualifications

Commissioning personnel must hold a Special Operation Certificate for High-Voltage Electricians. The high-voltage test link shall be operated by personnel with high-voltage test qualifications. The system of one person operating and one person monitoring shall be implemented throughout the process.

2. Tools and Instruments (Calibrated and Valid)

3. Document and Equipment Inspection

Document verification: Check the consistency between the switchgear factory test report, primary/secondary schematic diagrams, wiring diagrams, component nameplates (disjuntores, transformadores, protection devices, etc.) and design drawings;

Cabinet appearance: No deformation, intact paint finish, firmly installed components (no looseness of circuit breaker withdrawable chassis, disconnectors, earthing switches), firmly crimped wiring terminals with clear wire numbers, and no damage or contamination of insulating parts (bushings, insulators);

On-site environment: No debris around the cabinet, reliable grounding of foundation channel steel, normal ventilation/lighting in the distribution room, laid insulating mats, and complete warning signs for high-voltage operations.

4. Basic Grounding Test

Measure the cabinet grounding grid with a ground resistance tester, with the ground resistance ≤4Ω (main grounding grid of the substation). The cabinet is reliably connected to the foundation channel steel and grounding grid by copper busbar/flat steel, and the bolt torque complies with specifications (torque of M12 bolt ≥80N·m).

1. Unit Commissioning (Module-by-Module Test, Primary First Then Secondary, Mechanical First Then Electrical)

Unit commissioning refers to the independent split test of each component of the switchgear to eliminate faults of individual components/modules and lay the foundation for subsequent interlock commissioning. The core tests cover the circuit breaker unit, mutual inductor, secondary circuit and auxiliary components.

1. Commissioning of Circuit Breaker Withdrawable Chassis Unit (Core Primary Component)

KYN28 is a mid-mounted switchgear with a withdrawable circuit breaker, which is the focus of commissioning, including mechanical characteristic and electrical switching tests:

1. Mechanical operation of withdrawable chassis: Push/pull the chassis to the working position and test position, check whether the positioning pin is locked, the position indication (mechanical/electrical) is accurate, and the push/pull force is uniform without jamming;
2. Mechanical switching test: Conduct switching tests with a manual operating handle (no less than 5 vezes), check whether the circuit breaker is fully switched on and off, the moving contact stroke, overtravel and opening distance comply with the manufacturer’s technical parameters (the opening distance of vacuum circuit breaker is generally 11±1mm, overtravel 3±0.5mm), and the contact contact is good (contact gap measured by feeler gauge ≤0.1mm);
3. Electrical switching test: Apply the rated voltage (DC220V/AC220V, according to design) to the circuit breaker operating mechanism, perform inching switching through the secondary circuit, test the normal operation of the switching coil without abnormal noise, and the switching time meets the requirements (opening time of vacuum circuit breaker ≤60ms, closing time ≤100ms);
4. Mechanism energy storage test: Perform manual/electric energy storage, with mechanical/electrical indication after the completion of energy storage, no jamming of the energy storage mechanism, reliable holding after energy storage, and normal closing after release.
5. Commissioning of Disconnector/Earthing Switch
6. Manually operate the disconnector (static contact side) and earthing switch, check whether the switching is in place, the mechanical interlocking device is free of jamming, and the contacts are in tight contact;
7. Check whether the mechanical locking of the cabinet rear door takes effect after the earthing switch is closed (the rear door cannot be opened when the earthing switch is not open, a core requirement of KYN28 five-prevention);
8. Test the normal on-off performance of the position auxiliary contacts of the disconnector and earthing switch, which match the wiring of the secondary circuit (position signals can be uploaded correctly).
9. Commissioning of Mutual Inductors (Current Transformer CT/ Voltage Transformer PT)
10. Appearance and wiring: The mutual inductor is firmly installed with an intact insulating shell; the secondary side of CT is strictly prohibited to be open-circuited (short-circuited at the factory, check the integrity of the short-circuit piece during commissioning); the secondary side of PT is strictly prohibited to be short-circuited (equipped with fuse/air switch, check the integrity);
11. Insulation test: Measure the insulation of the primary side to the secondary side and to the ground of the mutual inductor with a 2500V megohmmeter, with insulation resistance ≥1000MΩ;
12. Transformation ratio verification: Test the CT/PT transformation ratio with a relay protection tester to be consistent with the nameplate/design (por exemplo, CT 600/5A, PT 10/0.1KV) with correct polarity (to avoid maloperation of protection).
13. Comprehensive Commissioning of Secondary Circuit

The secondary circuit is the core of control, protection and signal, which needs to be tested circuit by circuit. Commissioning of the secondary circuit is strictly prohibited when the primary circuit is live:

1. Insulation test: Measure the insulation of the secondary circuit to the ground and between each circuit with a 500V megohmmeter, with insulation resistance ≥1MΩ (the insulation resistance of weak current circuits such as measurement and control communication can be appropriately reduced but ≥0.5MΩ);
2. On-off and wiring verification: Verify the wiring circuit by circuit according to the secondary schematic diagram with the continuity gear of a multimeter, ensure the wire numbers are consistent with the drawings and the terminal crimping is free of virtual connection, with focus on verifying the switching circuit, protection circuit, energy storage circuit, position signal circuit and interlocking circuit;
3. Power supply circuit test: Apply the rated working voltage (DC220V/AC220V) to the secondary circuit, check the normal operation and stable voltage of each power supply module (por exemplo, protection device power supply, measurement and control power supply, lighting/heating power supply);
4. Auxiliary component test: Test the cabinet lighting, heater, temperature and humidity controller, condensation controller with action values in line with the design (por exemplo, the heater starts at ≥85%RH and stops at ≤70%RH); test the cabinet door travel switch and electromagnetic lock for normal operation.
5. Unit Commissioning of Protection Device/Measurement and Control Device

The protection device (microcomputer integrated protection, such as overcurrent, instantaneous trip, zero-sequence, PT disconnection protection) is the “brain” of the switchgear and shall be powered on and tested independently:

1. After the device is powered on, the self-test is normal without fault alarm, the interface display is clear, and the parameter setting interface can be operated normally;
2. Verify device parameters: The device address, CT/PT transformation ratio and communication parameters (por exemplo, Modbus) are consistent with the background system;
3. Key/remote control test: The local switching, reset and setting modification of the device operate normally, and the remote switching signal can be received/feedback normally.

III. Five-Prevention Interlocking Commissioning (Core Safety Requirement of KYN28, 100% Verification Mandatory)

The five-prevention mechanical + electrical interlocking of KYN28-12 is the key to preventing misoperation. The interlocking functions must be verified one by one during commissioning. Putting into use is strictly prohibited if any interlocking function fails. The core requirements and commissioning points of five-prevention are as follows:

1. Prevent opening/closing the disconnector with load: When the circuit breaker chassis is at the working position and closed state, the disconnector cannot be opened/closed and the chassis cannot be pulled out; the chassis can only be pulled to the test position and the disconnector can only be operated after the circuit breaker is opened;
2. Prevent misopening/closing the circuit breaker: When the chassis is not pushed to and locked at the working position/test position, the circuit breaker cannot be electrically switched on and off (manual operation is allowed for emergency according to the manufacturer’s design);
3. Prevent earthing with live circuit: When the circuit breaker chassis is at the working position (primary circuit live), the earthing switch cannot be closed; the earthing switch can only be closed when the chassis is pulled to the test position/out of the cabinet;
4. Prevent closing with earthing wire: When the earthing switch is closed, the circuit breaker chassis cannot be pushed to the working position and the circuit breaker cannot be closed;
5. Prevent entering live compartment by mistake: When the circuit breaker chassis is at the working position and the earthing switch is open, the mechanical locking of the front and rear cabinet doors cannot be opened; the rear door can only be opened after the earthing switch is closed, and the front door can be opened after unlocking (the unlocking key is managed by a dedicated person).

Commissioning method: Simulate various operation scenarios to verify the interlocking actions one by one, focus on checking the coordination of mechanical latches, position switches and electromagnetic interlocks, and ensure that all misoperation scenarios are effectively locked.

1. Power Frequency Withstand Voltage Test of Primary Circuit (Key High-Voltage Test, Eliminate Insulation Defects)

The withstand voltage test is the core test to verify the insulation strength of the primary circuit and shall be carried out after the completion of all unit and interlock commissioning. Safety isolation shall be well done before the test, the connection with other cabinets/equipment shall be removed, and the connection between the secondary circuit and the primary circuit shall be disconnected (por exemplo, the secondary side of the mutual inductor is short-circuited and earthed, and the protection device and measurement and control device are powered off).

1. Test Scope and Parameters (10KV KYN28 Standard)

The test object is the primary circuit of the switchgear (disjuntores, disconnectors, busbars, mutual inductors, bushings, etc.), including three parts: phase-to-phase, phase-to-ground and break tests. The test voltage is 42KV power frequency AC voltage with a duration of 1 minuto.

Phase-to-phase test: Apply voltage between phases A-B, B-C and C-A;

Phase-to-ground test: Apply voltage from phases A, B and C to the cabinet/ground respectively;

Break test: Apply voltage between the moving and static contacts when the circuit breaker is open (to verify the break insulation).

2. Qualification Standard

During the test, no breakdown, no flashover and no obvious discharge sound shall occur. After the test, retest the insulation of the primary circuit with a 2500V megohmmeter, and the test is qualified if the resistance has no obvious drop.

3. Notas

During the test, set up warning tape around the switchgear, strictly prohibit irrelevant personnel from entering, and the test personnel shall operate on the insulating mat;

After the test, fully discharge each phase of the primary circuit with a discharge rod and earthing it before restoring the wiring of the secondary circuit;

Lightning arresters and voltage transformers are strictly prohibited to participate in the power frequency withstand voltage test (test separately or remove them).

1. Protection Setting and Interlock Test of Protection Circuit

The protection settings shall be adjusted according to the design drawings/approval of the power supply department. Simulate faults with a relay protection tester to verify the interlock action of the protection device and the circuit breaker, ensuring reliable tripping in case of faults.

1. Setting Adjustment

Set the protection settings on the microcomputer protection device as required. Common protections and setting points of 10KV switchgear are as follows:

Overcurrent protection: instantaneous trip protection (no time limit, direct tripping for large fault current), time-limited instantaneous trip protection, overcurrent tripping protection (inverse time limit, delayed tripping for small fault current);

Zero-sequence protection: Aimed at single-phase earthing faults, the 10KV system is a small current earthing system, generally equipped with zero-sequence alarm/delayed tripping;

Other protections: PT disconnection protection, overvoltage/undervoltage protection (configured according to design).

Save the settings after adjustment and print the setting list for filing.

2. Simulated Fault Test (Core Interlock Link)

Connect the secondary side of CT/PT with a relay protection tester to simulate various fault conditions and test the protection actions:

1. Overcurrent instantaneous trip test: Input a current greater than the instantaneous trip setting value, the protection device shall act without time limit, send a tripping signal, the circuit breaker shall trip reliably, and the device shall record fault information;
2. Overcurrent delayed test: Input a current greater than the overcurrent setting value and less than the instantaneous trip setting value, the protection device shall act according to the set delay and the circuit breaker shall trip;
3. Zero-sequence protection test: Input zero-sequence current to verify that the zero-sequence alarm/tripping action meets the setting requirements;
4. PT disconnection test: Disconnect the PT secondary circuit, the protection device shall send a PT disconnection alarm in a timely manner without maloperation;
5. Protection reset/signal feedback: After fault tripping, the fault signal of the protection device is clear, the manual/automatic reset is normal, and the tripping signal can be uploaded to the background system (por exemplo, integrated protection cabinet in the distribution room, DCS system).
6. Remote Control/Background Interlock Test

If the switchgear is connected to the background monitoring system, test the functions of background remote switching and remote measurement/remote signaling:

Remote switching: The background system sends instructions, the circuit breaker can be switched on and off reliably, and the switching position signal is uploaded to the background system in real time;

Remote measurement: The background system can accurately display the current and voltage of the primary circuit (collected by CT/PT);

Remote signaling: The background system can display the circuit breaker switching position, chassis position, earthing switch position, fault alarm and other signals in real time.

1. No-Load Commissioning Run and Overall Acceptance
2. Inspection Before No-Load Commissioning Run

Restore all wiring removed during commissioning, check that there is no omission in the primary/secondary circuits, the setting list has been filed, and all five-prevention interlocks are effective;

Push the circuit breaker chassis to the working position, confirm the accurate position indication, open earthing switch, and close and lock the cabinet door.

2. Steps of No-Load Commissioning Run
3. The power supply department/operation and maintenance personnel shall operate to transmit power to the primary circuit of the switchgear (no-load, no load);
4. After power transmission, check that the cabinet has no abnormal noise, peculiar smell or discharge phenomenon, and the insulating parts have no heating;
5. Measure the no-load current with a clamp ammeter/background system, ensure the three-phase current is balanced without zero-sequence current;
6. Conduct no-load switching test: Perform electrical switching no less than 3 vezes, the circuit breaker operates normally, and the position signal and background feedback are accurate;
7. Commissioning run time: continuous no-load operation for 24 horas, the no-load commissioning run is qualified if there is no any fault or alarm during the period.
8. Overall Acceptance and Document Sorting

After the qualified commissioning run, conduct handover acceptance and sort out the complete set of commissioning documents for filing, including:

Switchgear factory test report and component qualification certificates;

On-site commissioning records (ground resistance, insulation resistance, withstand voltage test, mechanical characteristic, interlocking test records);

Protection setting list and protection device test records;

No-load commissioning run records;

Primary/secondary as-built drawings (mark the modified content if there is any revision).

VII. Safety Notes Throughout the Commissioning Process

1. The five-step operation method of power failure, electroscopy, earthing, hanging signboards and setting up barriers must be implemented for all high-voltage operations, and live commissioning is strictly prohibited;
2. A dedicated person must command the withstand voltage test and power transmission test, and the test plan must be formulated in advance with clear division of labor;
3. During the commissioning process, it is strictly prohibited to dismantle the five-prevention interlocking device without permission. If temporary dismantling is required, it must be restored immediately after the commissioning;
4. During the commissioning of the secondary circuit, it is strictly prohibited to short-circuit the AC voltage circuit and open the DC circuit to avoid damaging the protection device;
5. All test data must be recorded truthfully, forgery is strictly prohibited, and unqualified items must be rectified and retested until qualified.

VIII. Solução de problemas de falhas comuns (High-Frequency Problems in Commissioning)