High voltage testing is classified based on the purpose, type of voltage applied, and the nature of the test (destructive vs. non-destructive). Here's a structured breakdown of the main classifications of high voltage testing:
1. Based on Purpose
| Classification | Description |
|---|---|
| Type Tests | Performed on sample units to verify design compliance with standards. |
| Routine Tests | Done on every unit in manufacturing to ensure production quality. |
| Commissioning Tests | Done on-site before putting equipment into service. |
| Maintenance Tests | Done periodically to monitor insulation health during service life. |
| Special Tests | Customized tests for research, forensic analysis, or new conditions. |
2. Based on Nature of Voltage Applied
| Test Type | Voltage Type | Description |
|---|---|---|
| DC High Voltage Test | Direct Current | Applies constant polarity HV; used for cables, bushings. |
| AC High Voltage Test | Alternating Current | Applies power-frequency AC (50/60 Hz) or low-frequency AC. |
| Impulse Test | Impulse Voltage | Simulates surges (lightning, switching); very short duration. |
| Very Low Frequency (VLF) | Low-Frequency AC (0.1 Hz) | Low-power alternative for long cable insulation testing. |
| Oscillating Wave Test | Oscillating waveform | Used in diagnostic testing, often with partial discharge. |
3. Based on Destructive vs. Non-Destructive
| Classification | Goal | Description |
|---|---|---|
| Destructive Testing | Push to failure | Determines breakdown point (e.g., insulation puncture test). |
| Non-Destructive Testing | Evaluate integrity | Confirms insulation health without damaging the object. |
4. Based on Test Objective
A. Dielectric Strength Tests
Withstand (Hipot) Test: Apply overvoltage for a set time; no breakdown = pass.
Breakdown Test: Increase voltage until insulation fails (destructive).
B. Diagnostic Tests
Insulation Resistance (IR): Uses megohmmeter (DC); simple insulation check.
Capacitance and Tan Delta (Dissipation Factor): Measures dielectric loss.
Partial Discharge (PD) Measurement: Detects micro-insulation defects.
Time Domain Reflectometry (TDR): Locates faults in cables.
Oscillating Wave Test (OWTS): Low-energy PD testing on long cables.
C. Surge (Impulse) Tests
Lightning Impulse Test: Simulates 1.2/50 µs overvoltage (IEC/IEEE standard).
Switching Impulse Test: Simulates slow surges in EHV systems (e.g., 250/2500 µs).
5. According to International Standards
Many tests are defined in standards such as:
| Standard | Scope |
|---|---|
| IEC 60060-1/-2 | General HV test techniques |
| IEC 60502 / IEC 60840 | HV cable testing (AC, VLF, PD, etc.) |
| IEC 60076-3 | Transformer dielectric tests |
| IEEE 400 series | Field testing and evaluation of cable systems |
| IEC 60270 | PD measurement and test methods |
Summary Table
| Classification Method | Examples |
|---|---|
| By purpose | Type test, routine test, commissioning test |
| By voltage type | AC, DC, impulse, VLF, oscillating wave |
| By destructiveness | Destructive (breakdown), Non-destructive (withstand, PD) |
| By objective | Dielectric, diagnostic, surge simulation |
| By standard | IEC, IEEE, ANSI-based classification |