Substation Electrical Acceptance Test Case Report

On November 9, 2025, our technical team was invited to conduct electrical acceptance testing at:

Jiabiyou Food Raw Material Processing Co., Ltd.
(Ezhou Gedian Development Zone, Hubei Province, China)

The scope of work included:

• 2 high-voltage motors (1007 kW and 431 kW)
• 3 switchgear units
• Relay protection system commissioning verification

This project focused on pre-commissioning acceptance testing to ensure all equipment meets national electrical safety standards before energization.

Upon arrival at 11:00 AM, our engineers coordinated with the site maintenance engineer (Mr. Liu) and completed equipment inspection and test planning.

Key characteristics of the site equipment:

• High-power industrial motors without neutral line output
• Medium-voltage switchgear system
• Integrated relay protection control system

Due to system configuration, DC leakage testing on motors was not applicable. Alternative standard test methods were applied.

• Insulation resistance test (2500V)
• DC resistance test of windings
• AC withstand voltage test

• Insulation resistance: >5TΩ (maximum range reading at 2500V)
• DC resistance imbalance: <2% (phase balance qualified)
• AC withstand voltage test:
  • Voltage raised to 16kV for 1 minute
  • Standard reference: 2.5Un + 1kV for 10kV motors
  • No breakdown, no discharge, stable operation

✔ Motor insulation system fully qualified
✔ Winding condition normal
✔ Withstand voltage test passed

• Circuit breaker open-contact insulation test
• Closed-state insulation to ground
• AC withstand voltage test

• Insulation resistance reached maximum measurable limit
• No abnormal leakage detected
• AC withstand voltage test:
  • 42kV for 60 seconds
  • Voltage stable, no flashover or leakage

✔ All three switchgear units passed dielectric strength verification
✔ Mechanical and insulation condition confirmed safe

The relay protection systems were configured for:

• 2 motor protection circuits
• 1 transformer protection circuit

• Overcurrent protection
• Short-circuit protection (instantaneous trip)
• Overvoltage protection
• Undervoltage protection

• Input set to 0.95 × setting value → No operation
• Input set to 1.05 × setting value → Correct tripping

• Trip response accurate
• Time delay consistent with settings
• No false operation or failure detected

✔ Protection system reliability confirmed
✔ Coordination logic correct

During this acceptance test, we used professional high-voltage and diagnostic equipment, including:

Used for motor winding evaluation
???? Equipment:  HZB1202 DC Resistance Tester (20A)

• High current injection
• Fast stabilization
• High precision winding comparison

Used for motors and switchgear insulation evaluation

• 2500V test level applied
• High insulation condition confirmed

Used for insulation strength verification of motors and switchgear

???? Oil-immersed high voltage test system:

AC Withstand Voltage Test Equipment – Oil Immersed Transformer

Key functions used in this project:

• AC dielectric strength testing
• Switchgear withstand voltage verification
• Motor insulation stress testing
• Stable high-voltage output under load

After completing all tests, the following conclusions were confirmed:

• Motor insulation and winding condition are normal
• Switchgear dielectric strength fully qualified
• Relay protection system operates accurately
• No abnormal discharge or instability detected

✔ The entire electrical system meets commissioning requirements
✔ Safe for energization and operation

• Motors had no neutral line, DC leakage test not applicable
• High-capacity motors required careful voltage ramp control
• Switchgear test required stable 42kV withstand level
• Relay protection verified using step injection method (0.95 / 1.05)

All testing equipment used in this project is supported with:

• 24-month warranty
• Technical remote support
• Calibration service
• Spare parts supply
• Field application guidance

For substation commissioning testing, high-voltage testing solutions, or equipment selection support, please contact our engineering team.