ABB RED670 Line Differential Protection

The ABB RED670, also cataloged as the RED670 Line Differential Protection, operates as a dedicated hardware component for high-speed phase comparison and current differential calculation within power transmission networks. The device samples secondary analog current inputs from segmented instrument transformers to execute instantaneous fault trip routines across transmission grid infrastructures.

Hardware Specifications

Profinet / EtherNet/IP Deterministic Networks Performance

Differential trip calculations demand real-time data streaming that matches the backplane bus communication velocity of the central protection assembly. The high I/O density scaling of the RED670 hardware permits concurrent sampling of multiple CT inputs, mapping the values into synchronous telemetry frames. Maintaining strict firmware flash compatibility between the analog measurement cards and the active network communication blocks is mandatory to ensure zero-jitter pulse processing over deterministic communication rings.

Frequently Asked Questions

Q: Can the RED670 processing unit remain active during a hot-swap modification of the analog input module?

A: No. Hot-swapping the primary analog input hardware block is prohibited. Secondary current transformer circuits must be securely shorted and the auxiliary power isolated before extracting any internal board array to prevent high-voltage electrical arcing.

Q: What are the cable loop resistance limitations for the 100/5 A CT circuit configuration?

A: The single-direction run between the junction point and the furthest CT must use AWG10 cable under 100 ft, enforcing a total loop resistance limitation of approximately 0.1 Ohm at 75 deg C.

Q: Why must the CT ratios match across all designated terminal nodes?

A: The line differential algorithm calculates vector differences across the protected zone; mismatched ratio scales across line terminals will distort the balance equation and induce false trip execution under normal through-fault conditions.

Field Installation Guidelines

• Secondary Circuit Isolation: Ensure all current transformer inputs are connected via shorting-type terminal blocks. Never open-circuit an active CT secondary line during physical wireways terminal modification.
• Shielding and Grounding Architecture: Terminate all analog copper cables using standard twisted-pair shielded conductors. Ground the outer copper shield at a single point on the entry gland plate to prevent localized circulating currents.
• Cable Loop Length Validation: Restrict total loop runs to the calculated maximum foot boundaries (e.g., within 50 ft for AWG10 on 600-300/5 A arrays) to verify total resistance stays within the 0.05 Ohm single-way specification at 75 deg C.