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CT & PT Testing & Commissioning

Accuracy, Safety,
Reliability

In any electrical substation or switchyard, Current Transformers (CT) and Potential Transformers (PT) are among the most crucial components for measurement, metering, and protection.
Their accuracy ensures fault detection, relay operation, and energy accounting remain precise.

Our Testing Process Get Quote
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Why Testing CTs and PTs Before Commissioning is Essential

Measurement Accuracy

Errors in ratio or polarity can cause faulty protection relay operation or wrong billing

Safety Assurance

Ensures insulation integrity and prevents flashovers

Protection Reliability

Correct performance during faults avoids equipment damage

Regulatory Compliance

Meets statutory accuracy class requirements for metering and protection

Extended Service Life

Early fault detection prevents premature failure

Standards Compliance

IS, IEC, and CEA standards for voltage levels from 11 kV to 400 kV

Understanding CTs and PTs

Current Transformers (CTs)

  • Reduce high primary current to a proportional, measurable low current
  • Used for protection relays, control systems, and metering
  • Common accuracy classes: 0.1, 0.2, 0.5, 1, 3, 5P, 10P

Potential Transformers (PTs)

  • Step down high voltage to a safe, measurable level
  • Used for metering, control, and voltage-based protection schemes
  • Accuracy classes: 0.1, 0.2, 0.5, 1

Our CT/PT Testing & Commissioning Process

Comprehensive testing following IS 16227, IS 2705, IS 3156, IEC 61869 standards

1. Pre-Installation Checks

Visual Inspection:

Check for cracks, oil leaks, damaged terminals, or contamination

Nameplate Verification:

Confirm rated values, burden, and accuracy class match design requirements

Mechanical Alignment:

Ensure mounting structures and clamps are properly aligned

2. Electrical Testing

Insulation Resistance (IR) Test
Measures insulation quality between windings and earth
Polarity Test
Confirms correct polarity marking for accurate operation
Ratio Test
Compares actual transformation ratio with nameplate ratio
Excitation Curve Test (CTs)
Determines knee point voltage and core saturation characteristics
Burden Test
Measures load on secondary circuit within rated limits
High Voltage Withstand Test
Applies overvoltage to check insulation endurance

3. Functional Checks & Integration

  • Relay Coordination Check: Ensure signals are correctly integrated with protection relays
  • Metering Verification: Match readings with calibrated reference instruments
  • SCADA Integration: Confirm live data transmission to control centers

4. Commissioning Procedure

  • Energization: Gradual voltage/current application while monitoring readings
  • Fault Simulation: For protection CTs, simulate fault conditions to verify relay trip
  • Final Calibration: Fine-tune metering equipment connected to CT/PT secondaries
  • Handover Reports: Complete test reports and compliance certificates

Real-World Example

CT/PT Commissioning for 220 kV Switchyard in Rajasthan

28 CTs & 12 PTs

State Transmission Project - 2023

Project Highlights

Tests Performed: Ratio, polarity, burden, IR, accuracy verification

Challenge: Tight deadline and extreme summer heat conditions

Solution: Parallel testing teams and mobile test kits

4 Days

Ahead of schedule completion

100%

Compliance reports achieved

Benefits of Our CT/PT Testing & Commissioning Services

Accuracy Assurance

Precise readings for metering and protection

Operational Safety

Insulation and wiring verified before load application

Regulatory Compliance

Meets IS/IEC accuracy class mandates

Extended Equipment Life

Prevents early degradation and failures

Zero Downtime

Tested, integrated, and energized seamlessly

Performance Optimization

Maximum accuracy for all voltage levels from 11 kV to 400 kV