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ABB

ABB SPCD 3C21 Biased Single-Phase Differential Relay Module for Phase L1

SKU SPCD3C21

In stock

12-month warranty
Free returns within 30 days

Manufacturer: ABB
Product No.: SPCD3C21
Origin Sweden
Product Type: Differential Relay Module
Barcode: 85049099
Payment: T/T, Western Union
Weight: 0.32 kg
Shipping port: Xiamen
Warranty: 12 months

Product Description

Description

The ABB SPCD 3C21 is a biased single-phase differential relay module designed for phase L1 transformer differential protection.

The module measures the high-voltage and low-voltage side currents of the protected transformer. It calculates differential and stabilizing currents for protection decisions.

Transformer vector-group matching is configured through front-panel selector switches. Separate correction settings compensate for current-transformer ratios on the HV and LV sides.

The biased differential stage provides adjustable basic starting and stabilizing settings. An additional instantaneous high-set stage provides operation for high differential currents.

Second-harmonic restraint automatically blocks the differential stage when transformer inrush current is detected. The module also supports blocking inputs, trip outputs, event recording, self-supervision, and SPA bus communication.

Features

Biased single-phase differential protection
Designed for transformer phase L1
HV and LV current measurement
Differential current measurement
Stabilizing current calculation
Transformer vector-group matching
Independent CT ratio correction for HV and LV sides
Adjustable basic differential starting value
Adjustable starting ratio
Instantaneous high-set differential stage
Second-harmonic inrush restraint
External blocking input
Blocking signal output
Latched trip option
Front-panel measured-value display
Self-supervision alarm
Recorded trip and disturbance information
SPA bus communication

Applications

Power transformer differential protection
Three-phase transformer protection using one module per phase
HV/LV current comparison
Transformer inrush discrimination
Substation protection systems
SPACOM protection and control systems
Replacement of installed SPCD 3C21 relay modules

Technical Specifications

Parameter	Specification
Manufacturer	ABB
Model	SPCD 3C21
Product Type	Differential Relay Module
Protection Principle	Biased single-phase differential
Protected Phase	L1
Associated Phase L2 Module	SPCD 3C22
Associated Phase L3 Module	SPCD 3C23
Main Measurements	HV current, LV current, differential current
Communication	SPA bus
Self-Supervision	Integrated

Biased Differential Stage

Parameter	Specification
Basic Starting Value p	20 to 50% of In
Starting Ratio s	10 to 50%
HV-side CT Ratio Correction I1/In	0.5 to 1.0
LV-side CT Ratio Correction I2/In	0.5 to 1.0
Second-Harmonic Restraint Threshold	10 to 20% x Id
Operating Accuracy	±5% of set value
Operating Time	20 to 50 ms

High-Set Differential Stage

Parameter	Specification
Starting Current Id>>	20 to 30 x In
Operating Accuracy	±5% of maximum setting-range value
Operating Time	10 to 20 ms

Protection Functions

Function	Description
Biased Differential Protection	Operates from differential current with stabilizing-current restraint
High-Set Stage	Fast operation at high differential current
Second-Harmonic Blocking	Restrains operation during transformer magnetizing inrush
External Blocking	BS IN can block the differential stage
Blocking Output	BS OUT provides blocking to associated phase modules
Trip Signal	TS output provides trip indication
Latching	Selectable through switch SG1/7
Self-Supervision	Internal relay fault monitoring and alarm indication

Front-Panel Settings

Setting	Range / Function
p	Basic differential starting value, 20 to 50% of In
s	Starting ratio, 10 to 50%
I1/In	HV-side CT ratio correction, 0.5 to 1.0
I2/In	LV-side CT ratio correction, 0.5 to 1.0
SG1	Vector-group matching, latching, blocking mode, and related selections
STEP	Display navigation and setting access
RESET	Reset of indications and recorded information

Measured Data

Indicator	Measured Value
I1	HV-side load current as a multiple of relay rated current
Id	Differential current as a multiple of relay rated current
I2	LV-side load current as a multiple of relay rated current

Recorded Information

Register	Recorded Data
1	Differential current at the moment of tripping
2	Stabilizing current at the moment of tripping
3	Maximum stabilizing current after latest reset
4	Maximum second-harmonic current after latest reset
5	Filter calibration register
0	Blocking-mode status
A	Module communication address

Communication Data

Parameter	Specification
Communication System	SPA bus
Module Address	1 to 254
Data Transfer Rate	4800 or 9600 baud
Event Reporting	Supported
Remote Reading	Supported
Remote Setting	Supported with password
Password Range	1 to 999

Event Codes

Code	Event
E1	Harmonics blocking
E2	Harmonics blocking reset
E3	Tripping
E4	Tripping reset
E50	Restarting
E51	Event-register overflow
E52	Temporary data communication disturbance
E53	No response from module
E54	Module responds again

Transformer Vector-Group Matching

The SPCD 3C21 provides selectable transformer vector-group matching through switchgroup SG1.

The relay compensates for phase displacement between HV and LV currents without requiring external interposing transformers for the supported configurations.

The setting must match the actual transformer vector group and CT connection arrangement.

Installation & Commissioning

Verify that SPCD 3C21 is used for phase L1.
Confirm SPCD 3C22 and SPCD 3C23 assignments where a three-phase scheme is used.
Record all SG1 selector positions before replacing an existing module.
Confirm transformer vector group and CT connection before setting SG1.
Set HV and LV CT ratio corrections according to the installed current transformers.
Verify the basic starting value, starting ratio, harmonic restraint, and high-set settings.
Check BS IN, BS OUT, TS, and self-supervision functions before service.
Verify SPA communication address and baud rate where remote communication is used.

Replacement Notes

Match the exact SPCD 3C21 phase designation during replacement.
SPCD 3C21, SPCD 3C22, and SPCD 3C23 are assigned to phases L1, L2, and L3 respectively.
Preserve SG1 vector-group and blocking selections from the original installation.
Preserve protection settings and SPA communication parameters before removing the existing relay.

Shipping & Returns

Global Express Shipping

Standard Delivery: 4–6 business days via DHL, FedEx, and UPS.
Express Dispatch: Same-day dispatch for in-stock orders placed before 2:00 PM (GMT+8).
Worldwide Coverage: Serving over 150 countries.

Returns & Warranty

30-Day Guarantee: Returns accepted for in-stock products in original, factory-sealed packaging.
12-Month Warranty: Every industrial component is backed by our technical warranty.

FAQ

What is the ABB SPCD 3C21?

The ABB SPCD 3C21 is a biased single-phase differential relay module designed for phase L1 transformer differential protection.

What is the difference between SPCD 3C21, 3C22, and 3C23?

ABB assigns SPCD 3C21 to phase L1, SPCD 3C22 to phase L2, and SPCD 3C23 to phase L3 in a three-phase differential protection scheme.

Does the ABB SPCD 3C21 provide transformer inrush blocking?

Yes. The ABB SPCD 3C21 measures the second-harmonic component of differential current and blocks the differential stage when the configured restraint threshold is exceeded.

What is the setting range of the SPCD 3C21 differential stage?

The basic starting value is adjustable from 20 to 50% of rated current. The starting ratio is adjustable from 10 to 50%.

What is the high-set range of the ABB SPCD 3C21?

The instantaneous high-set differential stage is adjustable from 20 to 30 times the relay rated current, with an operating time of 10 to 20 ms.

Does the SPCD 3C21 support remote communication?

Yes. The ABB SPCD 3C21 supports SPA bus communication for event reporting, measured data, settings, recorded values, and remote setting functions.

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