A substation multiplexer is tested at two moments: at the factory (FAT), with the equipment and its configuration, and on site (SAT), already connected to the real links. The tests cover redundant power supply, alarms, control module switchover, optical power and sensitivity of each transceiver, Ethernet channels and teleprotection with its transfer time.
Two test moments
Short answer. A multiplexer is tested first at the factory (FAT) and then at the substation (SAT). The FAT confirms that the equipment and its configuration meet the engineering. The SAT confirms that, with the real fibers and remote equipment, each service works. This guide describes what those tests contain; the tests of the fiber network and of the complete scheme are in multiplexer and fiber optic network and in direct or multiplexed fiber for 87L.
The order and the boxes of an equipment test report from a multiplexer manufacturer such as the FOX615 serve as a map: each chapter corresponds to a type of module or service. A project protocol also adds the document list, the list of equipment and accessories, the list of test instruments and the punch list.
What is verified
| Block | What is checked |
|---|---|
| Power supply | Input to the chassis at the expected value; dual power supply with each feed switched on and off separately. In a project protocol, the two expected supply voltages (for example, AC and DC) |
| Fan unit and alarm | Power reconnection, urgent and non-urgent alarm on the output relay and on the LED, and each external alarm input |
| Control modules | Manual switchover between the active module and the standby module |
| Transport interface | Transceivers installed in each slot and port, transmit power and receive sensitivity, Ethernet channel per engineering, loss-of-signal alarm when the receive path is cut |
| Ethernet modules | Transceivers, optical levels, alarms with the signal operating normally and with the path cut |
| Teleprotection | Each module, its direction, trip voltage, times |
| IEEE C37.94 interface | Optical transmit power of the port, per that standard |
Optical levels of the transceivers
A multiplexer manufacturer’s report gives, for each SFP transceiver type, the expected transmit power range and the minimum receive sensitivity, which are recorded and compared with what is measured. Those values are used to calculate the budget of each link; an example with the figures of seven transceiver types is in fiber optic link budget.
In an alarm test, the receive fiber is cut and it is checked that the loss-of-signal alarm lights on the card and that the network element failure appears. This verifies that the equipment gives notice when a link is lost, not just that it transmits.
Teleprotection
Each teleprotection channel is tested separately. The report asks for recording, per channel, the trip voltage, the transfer time in milliseconds, the prolongation time and the transmit and receive direction. Unused channels are marked as available for a future connection.
The acceptance criterion for transfer time is set by the protection engineering and the scheme type; see teleprotection schemes and redundant teleprotection channels.
What changes between FAT and SAT
- Review of documents and equipment. Against the bill of materials and the engineering
- FAT at the factory. Power supply, alarms, modules, optical levels and channels
- Installation on site. Real fibers and remote equipment
- SAT on site. Optical levels and alarms are repeated with the real links
- End-to-end tests. Teleprotection and line differential with the relays
In the SAT the levels are measured again with the installed fibers and the services are tested with the equipment at the other end. If the level of a port changes between the FAT and the SAT, the most likely cause is the installed fiber link, not the equipment.
Records that must remain
- Signed report with management software version, configuration file and equipment addresses.
- Optical levels per port, with the transceiver type.
- Result of each alarm tested.
- Times of each teleprotection channel.
- Punch list, with owner and date.
These records are the evidence that the equipment was tested and of how it was left.
Multiplexer testing with Tiza Group
Are you going to receive or commission a multiplexer and need tests with evidence? At Tiza Group we include them in our commissioning and complete them with end-to-end tests of the teleprotection and of the 87L.
Related guides
- FOX615, FOX515, JungleMUX and TN1U multiplexers
- Multiplexer and fiber optic network
- Direct or multiplexed fiber for 87L
- Fiber optic link budget
- IEEE C37.94
- Teleprotection equipment
References
- FOX615 multiplexer manufacturer: equipment test report format (chapters on power supply, alarms, control modules, transport interface, Ethernet modules and teleprotection).
- IEEE C37.94: optical interface between teleprotection equipment and multiplexers.
Frequently asked questions
What is the difference between the FAT and the SAT of a multiplexer?
The FAT is done at the factory or workshop with the equipment mounted in its cabinet and the final configuration, and verifies the equipment against the engineering documentation. The SAT is repeated at the substation with the real fibers and remote equipment, and verifies that the services work end to end.
Why is the optical power of each transceiver measured?
Because each transceiver type has an expected transmit power range and a minimum receive sensitivity. If the measured level is outside the range, the link may work today and fail with the first additional fiber loss.
Is teleprotection tested inside the multiplexer?
Yes. Each teleprotection channel is verified with its trip voltage, transfer time and prolongation time, and it is checked that the channel goes to the intended direction.