Technical Characteristics of Three Channel Dc Resistance Testing

1、 Principle of efficient three-phase synchronous measurement

Three phase synchronous power on and independent sampling

By designing a dual power supply structure, a current (such as 20A) is applied to the three-phase winding of the YN connected transformer, and real-time data is collected using an independent three channel current/voltage sampling system. This design reduces the time required for traditional single-phase sequential measurement to about one-third, making it particularly suitable for fast tap changer testing of on load tap changers.

Example: Traditional methods require 15 minutes per phase to measure a 750MVA transformer, while three channel technology only takes 5 minutes to complete three-phase measurement.

Isolation measurement of neutral point lead resistance

When measuring three channels, the neutral point lead resistance (such as Roo ') is excluded from the results and the true winding resistance (RA, RB, RC) is directly obtained. This characteristic makes the test data for high-voltage windings (with high resistance) more accurate, but may affect the comparability of data on the low-voltage side (with low resistance) by ignoring the lead resistance.

2、 Intelligent operation and multifunctional integration

Adaptive output and multi-mode compatibility

Automatically select the optimal test current (0.1 μ Ω -100 Ω) based on the winding resistance, support three-phase synchronization or traditional single channel mode, and have built-in temperature conversion function (copper/aluminum wire coefficient) to meet different scene requirements.

Automation of Data Management and Analysis

Real time calculation of three-phase resistance imbalance rate, directly determining winding defects (such as broken strands, poor contact).

Store 500-10000 sets of data, support USB export or printing, and can annotate information such as phase sequence and tap position.

3、 High precision and wide range performance

Accuracy: 0.2% ± 0.5 μ Ω, resolution up to 0.1 μ Ω, capable of detecting small resistance changes.

Range coverage: 0-100 Ω (such as TP_SD3045B type), suitable for distribution transformers to ultra-high voltage transformers.

Anti interference and stability: Ripple coefficient ≤ 0.5%, ensuring stable test data on the low voltage side of large capacity transformers.

4、 Security protection design

Multiple protection mechanisms

Discharge alarm and automatic demagnetization: After the test is completed, the discharge status is indicated through the sound system to prevent misoperation; Built in nonlinear discharge circuit (resistance increases from small to large), accelerating energy release.

Reverse electromotive force protection: anti arc design to avoid the risk of arc when the test line is disconnected.

Environmental adaptability

Working temperature -20 ℃ -50 ℃, humidity ≤ 85% RH, industrial chassis shockproof design, suitable for complex outdoor environments.

5、 Applicable scenarios and limitations

Advantage scenario: Fast full tap testing of YN windings on the high voltage side and on load tap changers.

Not applicable:

Low or medium voltage star winding (data distortion caused by ignoring the neutral point lead resistance).

Factory factory test (including complete data on lead resistance).

HZ-3320D 20A Three-channel DC Resistance Tester