LCD-17 type transformer differential relay is a kind of relay produced by Chunxing Electric Power Technology. It is made of differential current principle and can detect the following faults: three-phase or two-phase short circuit of transformer internal winding, ground fault of transformer with directly connected neutral point or low resistance, and short circuit between or between transformer windings.
The LCD-17 differential relay provides primary protection for single‑sided power substations, detecting internal short‑circuit, ground, inter‑turn and inter‑layer faults in two‑, three‑, and auto‑transformers. The document details its structure, principle of operation, and the various protection functions.
It also covers technical specifications, adjustment of current‑balancing taps, testing procedures for braking and harmonic suppression, inspection steps, and ordering information, enabling proper installation, commissioning, and service of the relay. This manual is written in Chinese.
| Rated current (In) | 5 A, 50 Hz |
|---|---|
| Brake coefficient range (KZ2) | 0.4 – 0.6 |
| Power consumption (differential circuit) | ≤ 1.5 VA |
| Power consumption (brake circuit each side) | ≤ 0.8 VA |
| Action time (main circuit, 0.5× setting) | 40 ± 5 ms |
| Action time (fast differential circuit, 1.5× setting) | ≤ 15 ms |
The relay is rated for 5 A at 50 Hz.
The proportional brake coefficient can be set between 0.4 and 0.6.
Under rated current the differential circuit consumes no more than 1.5 VA, and each side of the brake circuit no more than 0.8 VA.
The fast differential circuit operates in 15 ms or less.