Beijing Sifang CSC-241B Digital Transformer Backup Protection and Control Device

1.1 Device Introduction

This device is suitable for backup protection and control of large and medium-sized transformers at voltage levels of 66kV and below. It is configured per side and can be installed locally in switchgear.

For large transformers (2000kVA and above), it generally needs to form a complete protection system with the CSC-241A differential protection device from the same series.

1.2 Main Functions

1.2.1 Main Protection Functions

Three-stage composite voltage-blocked overcurrent protection, where undervoltage blocking and negative-sequence voltage blocking can be individually enabled or disabled for each overcurrent stage. Composite

voltage blocking can be configured via control word to use either local-side voltage or remote-side voltage;

Cooling fan start function;

Tap changer blocking function;

Overload alarm;

Programmable output logic setting control;

Independent tripping circuit and fault recording.

1.2.2 Measurement and Control Functions

15 channels of digital input for telemetry collection, device status change telemetry, and fault telemetry

 Normal circuit breaker remote open/close control

 Telemetry of analog quantities such as Ua, Ub, Uc, Ia, Ib, Ic, P, Q, COSф, Uab, Ubc, Uca

 Various event SOE, etc.

 2 channels of pulse P, Q input

1.3 Protection Components

1.3.1 Overcurrent Protection

The device performs real-time calculation and three-stage overcurrent discrimination, each stage having an independent time delay. The current and time settings for each stage can be independently set, and the enabling or disabling of each stage can be controlled via control words.

When performing three-stage overcurrent discrimination, the logic for each stage is consistent, with the operation logic as shown in the overcurrent protection diagram on the next page.

1.3.2 Undervoltage Blocking

Activates when any of the three line voltages falls below the undervoltage setting, releasing the blocked protection elements. The control word can determine whether each of the three overcurrent stages is subject to undervoltage blocking.

1.3.3 Negative-Sequence Voltage Blocking

Calculated from the three line voltages. When the negative-sequence voltage exceeds the negative-sequence overvoltage setting, it releases the blocked protection. It can be used in conjunction with the undervoltage blocking element