Manufacturer: ABB
Product No.: SPCD3C21
Country of origin:Sweden
Product Type: Differential Relay Module
Barcode: 85049099
Payment: T/T, Western Union
Weight: 320g
Shipping port: Xiamen
Warranty: 12 months
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.
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
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
| 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 |
| 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 |
| Parameter | Specification |
|---|---|
| Starting Current Id>> | 20 to 30 x In |
| Operating Accuracy | ±5% of maximum setting-range value |
| Operating Time | 10 to 20 ms |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
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.
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.
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.
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Returns & Warranty
Global Express Shipping
Returns & Warranty
Orders are processed and delivered Monday-Friday (excluding public holidays).
For full eligibility, restocking fees, and international return details, please view our official Refund & Return Policy .
| Country of origin |
Sweden
|
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