Classification of Equipment Defects for Relay Protection and Safety Automatic Devices in Substations

In daily operations, various equipment defects are inevitably encountered. Whether maintenance personnel, operation and maintenance staff, or specialized management personnel, all must understand the defect classification system and adopt appropriate measures according to different situations.

According to Q/GDW 11024-2013 "Operation and Management Guide for Relay Protection and Safety Automatic Devices in Smart Substations," equipment defects are classified into three levels based on severity and the threat they pose to safe operation: critical, serious, and general.

1. Critical Defects

Critical defects refer to those with severe nature and urgent conditions that directly threaten safe operation. Emergency measures should be taken immediately, and resources organized to eliminate them. Critical defects include:

a) Electronic transformer (including acquisition unit) failure;

b) Merging unit failure;

c) Intelligent terminal failure;

d) Process layer network switch failure;

e) Protection device failure or abnormal withdrawal;

f) Abnormal pilot protection channel with inability to send/receive data;

g) SV, GOOSE disconnection and abnormal status changes in input quantities that may cause incorrect protection operation;

h) Control circuit disconnection or DC power loss in control circuit;

i) Other situations directly threatening safe operation.

2. Serious Defects

Serious defects refer to those with severe conditions showing deterioration trends that affect correct protection operation, posing threats to power grid and equipment safety, and potentially causing accidents. For serious defects, the corresponding protection may be requested to be withdrawn when specialized maintenance personnel arrive on site. During the period before defect handling, on-site operators should strengthen monitoring and take timely measures when protection misoperation risks exist. Serious defects include:

a) Increased attenuation in pilot protection channels exceeding 3dB; significantly abnormal frame loss in pilot protection channels;

b) Protection device only issuing abnormal or alarm signals without blocking protection;

c) Fault recorder or process layer network analyzer device failure or power loss;

d) Indicator lights on operating box not illuminated but without control circuit disconnection signal;

e) Incomplete or missing accident reports after protection device operation;

f) Normal local signals but abnormal background or central signals;

g) Communication interruption of protection information in unattended stations;

h) Abnormal auxiliary contact inputs of busbar protection isolating switches, but not affecting correct operation of busbar protection;

i) Communication anomalies between substation and main station of relay protection fault information system, between substation and protection devices, between substation and integrated monitoring system, as well as self-check anomalies of the substation;

j) Defects that occur frequently but can automatically recover;

k) Other situations that may affect correct protection operation.

3. General Defects

General defects refer to those other than critical and serious defects, with ordinary nature, relatively minor conditions, allowing protection to continue operating with minimal impact on safe operation. General defects include:

a) Inaccurate time or uncalibratable clock in protection devices;

b) Poor contact of buttons on protection panels;

c) Abnormal liquid crystal display on protection devices;

d) Communication interruption of protection information in attended stations;

e) Occasional defects that can automatically recover;

f) Other defects with minimal impact on safe operation.