XHYZ1668T On-Load Tap Changer Tester| Transition Resistance & Waveform Analyzer
The on-load tap changer is the only moving part connected to the transformer circuit, which is why OLTC inspection is taken so seriously. Handover and preventive test procedures for electrical equipment require verification of the tap changer action sequence and switching time. The XHYZ1668T measures the OLTC transition waveform, transition time, instantaneous transition resistance values and three-phase synchronization in one test. With 20kHz sampling, a 7-inch LCD, complete protection circuits and a main unit weighing only 6.15kg, it is the practical choice for engineers who must prove tap changer performance on site and after every overhaul.
Applications & Target Audience: Engineered for substation construction and commissioning contractors, power engineering EPC companies, and transformer overhaul & repair workshops that must verify OLTC action sequence, transition time and transition resistance during handover acceptance tests, after tap-changer maintenance, and before transformers return to service.
Key Specifications
| Parameter | Specification |
|---|
| Output Current | 1.0A / 0.5A / 0.2A |
|---|
| Transition Resistance Range | 0.3Ω ~ 20Ω (1.0A)
5Ω ~ 40Ω (0.5A)
20Ω ~ 100Ω (0.2A) |
|---|
| Transition Time Range | 0 ~ 320ms |
|---|
| Open Circuit Voltage | 24V |
|---|
| Measurement Accuracy | Transition resistance: ±(5% reading ±0.1Ω)
Transition time: ±(0.1% reading ±0.2ms) |
|---|
| Sampling Rate | 20kHz |
|---|
| Data Storage | 500 groups built-in |
|---|
| Display | 7-inch high-brightness LCD |
|---|
| Output Interfaces | High-speed printer, USB port, RS232 serial port |
|---|
| Dimensions | Main unit: 360 × 290 × 170 mm
Cable box: 360 × 290 × 170 mm |
|---|
| Weight | Main unit: 6.15kg
Cable box: 4.55kg |
|---|
| Ambient Temperature | -10°C ~ +50°C |
|---|
| Ambient Humidity | ≤85% RH |
|---|
| Working Power Supply | AC 220V±10%, 50±1Hz |
|---|
Advanced Features
- High output current (1.0A) with a lightweight main unit of only 6.15kg
- Tests YN, Y and Delta connected transformers with resistance values displayed directly without conversion
- Supports both with-winding and without-winding measurement methods
- Waveform display automatically adjusts resistance and time amplitude according to sampled values
- Complete protection circuit for high reliability in field use
- 7-inch high-brightness LCD with clear menu-driven operation for on-site work
- Built-in storage for 500 groups of test data with query and print functions
- High-speed built-in printer plus USB and RS232 interfaces for data export
- 20kHz high-speed sampling captures every detail of the OLTC switching waveform
- Waveform analysis identifies typical OLTC defects such as slow operating mechanisms, broken transition resistors and loose connections
- Automatic waveform evaluation with manual cursor-based verification for printing and reporting
Waveform Diagnosis: Typical OLTC Fault Patterns
The XHYZ1668T records the complete switching waveform so that engineers can judge the health of the tap changer, not just pass or fail a resistance reading. The instrument evaluates the following waveform parameters:
| R0 | Coil resistance plus test lead resistance |
|---|
| R1 / R2 | Transition resistor 1 / transition resistor 2 |
|---|
| T0 | Three-phase synchronization (referenced to the first detected phase) |
|---|
| T1 / T3 | Running time of transition resistor 1 / transition resistor 2 |
|---|
| T2 | Bridge time |
|---|
| T4 | Total transition time |
|---|
Typical fault patterns detected by waveform analysis:
- Slow mechanism (spring aging): pre-bridge time extends to about 50ms on all three phases, roughly three times normal, indicating a tired quick-action spring that must be replaced.
- Broken transition resistor: a symmetric zero-crossing segment appears on the odd-number side with resistance reading above 50Ω, which can be treated as an open circuit.
- Measurement oscillation: waveform oscillation caused by excessive trigger sensitivity on the inductance-increasing direction; reduce sensitivity and re-test from the 1-n direction.
- Broken strands in the selector lead: messy waveform with transition resistance as low as 0.3-0.5Ω across all taps, caused by a partially broken flexible connection shorting the transition resistor.
FAQ
Q1: Who is the XHYZ1668T on-load tap changer tester designed for?
It is designed for substation commissioning contractors, power engineering companies and transformer overhaul workshops that perform handover acceptance tests and post-repair verification of on-load tap changers on power transformers.
Q2: Which tests does it support for handover acceptance?
It checks the OLTC action sequence, measures transition waveform, transition time, instantaneous transition resistance of each phase and three-phase synchronization, covering the tap changer items required by handover and preventive test procedures.
Q3: Which transformer connections can be tested?
YN, Y and Delta connected transformers can be tested with or without winding. For Y-connected transformers whose neutral is not led out, and for Delta windings, two-phase or single-phase methods with built-in resistance conversion formulas are provided.
Q4: How does waveform analysis help after an OLTC overhaul?
After repair, the waveform verifies that transition resistors, quick-action springs and selector contacts work correctly. Abnormal patterns such as extended bridge time, open transition resistors or shorted resistors are clearly visible, so the workshop can confirm the repair before the transformer returns to service.
Q5: What is included in delivery and after-sales service?
Each set includes the main unit, cable box with complete test leads, power cable, ground wire, fuses, printer paper and a user manual, packed in a wooden box. Delivery takes 5-8 working days, with a 12-month warranty and lifetime technical support.
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