Product Core Brief

• Model: SPAJ110C
• Brand: ABB
• Series: ABB SPACOM SPAJ 110 C earth-fault relay family
• Core Function: Selective earth-fault protection relay for solidly earthed or low-resistance earthed power systems; provides primary or backup earth-fault protection for feeders, transformers, generators, and motors.
• Product Type: Earth-fault protection relay
• Key Specs: Low-set I₀> (IDMT or definite-time) + high-set I₀>> (definite-time) | Serial interface | Self-supervision | Legacy ABB component
• Condition: New Original / New Surplus (verify by full order code and suffix)

Key Technical Specifications

• Part Number:
• Product Type: Earth-fault protection relay (SPACOM family)
• System Role: Provides selective earth-fault protection as primary or backup protection in solidly earthed or low-resistance earthed power systems
• Protection Stages: Two-stage neutral overcurrent — low-set I₀> and high-set I₀>>
• Time Characteristics: Low-set I₀>: definite-time or inverse-time (IDMT); High-set I₀>>: definite-time only
• Auxiliary Supply Voltage: Typically 80–265 V AC/DC (SPTU 240 S1) or 18–80 V DC (SPTU 48 S1); verify against the actual relay nameplate
• Frequency: 50/60 Hz (per order)
• CT Input: 1 A or 5 A rated current (verify against nameplate)
• Outputs: Typically 2 heavy-duty trip relays + 4 signal relays (configurable); verify against the actual unit
• Communication: Serial interface for connection to fiber-optic object bus and substation/network control systems
• Self-Supervision: Continuous hardware and software auto-diagnostics
• Mounting: Flush or semi-flush panel mounting; IP54 enclosure degree of protection for panel-mounted relay
• Lifecycle Status: Not active product since 2009; spare parts supply only

Product Introduction (No Fluff)

The ABB SPAJ110C is an earth-fault protection relay from the SPACOM family, designed for selective earth-fault protection in solidly earthed or low-resistance earthed power systems. It provides two protection stages — a low-set I₀> stage with definite-time or IDMT characteristic and a high-set I₀>> stage with definite-time characteristic — making it suitable as primary or backup earth-fault protection for feeders, transformers, generators, and motors.

Its practical value is maintaining legacy ABB distribution automation and substation installations where a failed earth-fault relay can compromise ground-fault selectivity and coordination. The relay can be configured to cooperate with a residual voltage relay for blocking/deblocking operation. For maintenance replacements, the full order code (e.g., SPAJ110C RS 421 010/210 -AA, -CA, -DA, -FA) and auxiliary voltage suffix should be matched against the existing relay label, since power supply range, test adapter configuration, and communication options may differ across variants.

QA & Testing SOP (Dynamic & Transparent)

For legacy earth-fault relays, we verify mechanical integrity and basic readiness before shipping.

1. Part number verification — Confirm SPAJ110C and the full order code/suffix on the label; check auxiliary voltage marking.
2. Visual inspection — Inspect the front panel, display, connectors, terminal blocks, and mounting clips for corrosion, burn marks, or mechanical damage.
3. Connector and terminal check — Verify CT input terminals, trip/signal output terminals, serial communication port, and auxiliary supply terminals for oxidation, loose contacts, or contamination.
4. Insulation and short-circuit check — Confirm no short circuits between CT inputs, auxiliary supply, and output circuits before energizing.
5. Power-up verification — Where test fixtures are available, apply rated auxiliary voltage and verify display, LED indicators, relay self-test, and output operation; pack with terminal protection.

Installation Pitfalls & Guide (Engineer to Engineer)

❗ Match the full order code and suffix. SPAJ110C variants differ in auxiliary voltage (e.g., 80–265 V AC/DC vs. 18–80 V DC), test adapter configuration, and communication options. Substituting without verification can cause wiring or compatibility mismatches.

❗ Verify CT polarity and zero-sequence connection. Incorrect CT polarity or residual current connection can cause false trips or failure to detect earth faults.

❗ Confirm auxiliary supply voltage. The relay supports multiple auxiliary voltage ranges depending on the power supply module installed. Verify against the nameplate before energizing.

❗ Back up relay settings. Before replacement, record all protection settings, including I₀> and I₀>> pickup values, time delays, IDMT curve selection, and blocking/deblocking configuration.

❗ Test with secondary injection. After installation, verify both earth-fault stages, trip/signal outputs, serial communication, and self-supervision functions using secondary injection testing before returning the feeder or transformer to service.

Replacement steps:

1. Record all relay settings, CT ratios, wiring connections, and communication configuration.
2. Remove auxiliary supply and verify zero voltage before disconnecting CT and trip circuits.
3. Install the replacement SPAJ110C with the same full order code and restore all settings.
4. Apply auxiliary supply, verify self-test, and perform secondary injection testing on both earth-fault stages.

Technical FAQ

What does the SPAJ110C do? It is an earth-fault protection relay providing selective ground-fault protection with two stages (I₀> and I₀>>) for feeders, transformers, generators, and motors in solidly or low-resistance earthed systems.

What is the difference between SPAJ110C variants? Variants differ in auxiliary supply voltage range (e.g., 80–265 V AC/DC vs. 18–80 V DC), whether a test adapter RTXP 18 is included, and communication/interface options. The full order code on the nameplate should always be confirmed before ordering.

Can it coordinate with a residual voltage relay? Yes. The relay can be configured to cooperate with a residual voltage relay for blocking/deblocking earth-fault operation.

Is it still available? It has been a non-active product since 2009. New surplus and verified replacements can be sourced, but long-term projects should evaluate migration to a supported ABB protection relay platform.