Marine and Offshore Relay Testing
A ship is an island grid. The generators are the only source, the bus is short, the fault current is limited and the consequences of a wrong trip are immediate. Protection testing on board is therefore a mix of generator protection, preferential trip, blackout recovery and shore-connection protection. A relay test set covers the relay and controller side of all four; the class society and the real blackout test cover the rest.
What is tested on board
| Test object | Functions and logic | Injection and I/O | Recommended |
|---|---|---|---|
| Generator protection | 32 reverse power, 40 loss of field, 46 negative sequence, 51V, 64G, 81O/U, 87G differential | Three or six currents, three or six voltages, trip and alarm outputs | VAE-660 for 87G; VAE-430 for single-ended |
| Preferential trip and load shedding | Frequency and voltage thresholds, stage outputs, non-essential load trip | V and f outputs, binary inputs for stage commands | VAE-430 or VAE-660 |
| Blackout auto-start sequence | Dead-bus detection, emergency generator start, breaker close, load restoration | Voltage and frequency simulation, status contacts, timing | VAE-660 for multi-source sequences |
| Main switchboard and feeder protection | 50/51, 51N, 27/59, 81, interlocking | Three currents, three voltages, binary I/O | VAE-430 |
| Shore connection protection | IEC/IEEE 80005-1 interface: voltage, frequency, phase sequence, protection and interlock | Three-phase V/I, phase and frequency control, status I/O | VAE-660 for the full interface |
| Transformer and thruster feeder protection | 87T, 50/51, 51N, 27/59 | Six currents for 87T; three for feeder | VAE-660 for 87T; VAE-430 for feeder |
Why the generator differential decides the model
Marine generator protection almost always includes 87G, and 87G needs six current channels: three on the neutral side and three on the line side. The VAE-430 has three current channels, so it can prove single-ended elements but not the differential slope and harmonic restraint. The VAE-660 has six current and six voltage channels, which also covers the two live sources needed for a blackout or shore-connection sequence. For a shipyard or a service company working on generator protection, the VAE-660 is the instrument that avoids a second visit.
Blackout recovery: what can be simulated
The blackout sequence is a state machine: dead bus, emergency generator start, voltage and frequency build-up, breaker close, load restoration in stages. A test set can reproduce the voltage and frequency states, emulate the breaker and bus status contacts, and time every command. It can prove that the logic, the thresholds and the delays are correct.
It cannot prove that the real emergency generator starts, reaches voltage and accepts load in the required time. That is a live blackout test with the actual generator, the actual load and the class surveyor. The two tests answer different questions and one does not replace the other.
Class society boundaries
| Requirement | What the test set can do | What it cannot do |
|---|---|---|
| Annual blackout test | Verify the logic and timing of the auto-start and restoration sequence | Replace the real blackout required by the class society |
| Generator protection survey | Inject and verify all electrical protection functions | Witness the test on behalf of the class society |
| Shore connection approval | Verify protection, phase sequence, voltage and frequency limits at the interface | Certify the shore connection installation or the cable system |
| Switchboard FAT | Test protection and control logic at the panel builder | Replace the sea trial and the class witness |
Onboard practicalities
- Space and power. The test set is 18 kg or 21 kg and runs from a standard 230 V or 120 V socket. On board, the available socket and the cable route often decide the test plan more than the channel count.
- Long leads. Generator and switchboard tests can need long current leads. Burden and lead resistance matter; the parallel output and the per-phase power of the test set set the limit.
- Documentation. Class surveys and yard handover expect test records per relay, with settings, injection values and results. The report format should be agreed before the test, not after.
- DC control. Marine control systems are usually 24 V DC. The programmable DC output covers that with margin; 220 V DC coils need the station battery or a separate source.
Frequently asked questions
Can the VAE-430 test marine generator protection?
It covers single-ended functions: overcurrent, voltage-restrained overcurrent, reverse power, loss of field, negative sequence and frequency. Generator differential 87G and multi-source blackout sequences need the VAE-660.
Can the test set replace the annual blackout test?
No. It verifies the logic and timing of the sequence. The class society requires a real blackout with the actual generator and load, witnessed by the surveyor.
Can it test shore connection protection?
Yes, at the protection and control interface: voltage, frequency, phase sequence, protection settings and interlock logic. It does not certify the shore connection installation or the cable.
Does it support 50 Hz and 60 Hz ship systems?
Yes. The source covers 0–1000 Hz in PC mode, including 50 Hz and 60 Hz.
What about 400 Hz on specialised vessels?
The frequency range covers 400 Hz. Aviation-style 115/200 V three-phase 400 Hz equipment is a different qualification and is not a marine application.