A trip matrix is the controlled translation from detected condition to physical outputs. It identifies every breaker, lockout relay, alarm, interlock and reclose block required for each protection or control event.

Learning objectives

Create an auditable logic design, separate trips from alarms and prove that every output has one defined owner and fail-safe state.

Core engineering principles

Rows are initiating conditions, columns are actions

Each relay function, external trip, pressure contact or breaker-failure stage is mapped to breaker coils, lockout, SCADA, recording and blocking outputs.

Trip and lockout are different actions

A direct trip opens a breaker; lockout retains a reset-required state and often trips multiple devices. The philosophy must justify which faults latch.

Reclose and transfer must be blocked selectively

Bus, transformer, breaker-failure and internal equipment faults normally require different post-trip behaviour from transient feeder faults.

Fail-safe logic depends on signal type

Normally energised and de-energised contacts respond differently to broken wires and supply loss. Naming a signal “healthy” is not enough; its de-energised meaning must be explicit.

Hardwired and GOOSE logic need the same matrix

Communication technology changes transport, not functional ownership. Quality, timeout and fallback behaviour must be included.

Engineering application method

  1. Step 1: List every initiating event and source IED.
  2. Step 2: Define required trips, lockout, alarms and blocks.
  3. Step 3: State contact logic, pulse or latch, and reset method.
  4. Step 4: Allocate physical outputs or GOOSE messages and ownership.
  5. Step 5: Test each row through the complete trip chain and record evidence.

Practical example

Transformer differential may trip both HV and MV breakers, operate lockout and block auto-reclose. A winding-temperature alarm may only signal, while a high-high contact trips selected devices. The matrix prevents these actions being hidden across multiple drawings.

Common mistakes

  • Combining alarm and trip rows ambiguously.
  • Omitting reclose blocking.
  • Leaving reset responsibility undefined.
  • Mapping one output to two owners.
  • Changing GOOSE dataset without logic regression testing.

Design and review checklist

  • Does every event have one defined action?
  • Are all breakers and coils identified?
  • Are latching and reset rules clear?
  • Is fail-safe state documented?
  • Can every row be end-to-end tested?

Standards basis and official sources

Engineering note: Verify the contracted standard edition, amendments, manufacturer evidence and project-specific studies before applying these principles to a supplied assembly.

Similar Posts