Tele protection

Northern Power Grid
Scanlink / Sentinel Digital Radio
Tele protection
Industry / Vertical:

Power failures and resultant blackouts are not common in the UK today, though they do still occur, and while there are a number of causes, the two most common are severe weather bringing down power lines, and cable theft.

To avoid power outages, cables ring cities, from substation to substation, with current transformers monitoring power leaving and arriving each substation. In normal operations the current should remain identical whilst the voltage will fluctuate. When an abnormal event happens, such as a tree falling on a power line, it will affect the power balance between substations which can be detected. If a cable falls and earths for example, the current will climb at the delivering substation, while the receiving substation will get nothing. In this scenario the sub stations need to be switched out very quickly to isolate the line and avoid further damage to the network - every fraction of a second counts.

The Challenge

Traditionally in the UK the copper wiring which provides the required constant, <70 millisec reaction for protection of the electricity supply network was supplied by BT. But with the arrival of the new BT 21CN (fibre Ethernet) unknown latency and routing will no longer support substation measuring after 2015. This is an immediate challenge for electricity companies throughout the UK, including Northern Power Grid, which is responsible for delivering electricity safely and reliably to 3.8 million customers across northeast England, Yorkshire and northern Lincolnshire.

The Solution

The need to find an alternative that can deliver the necessary speed of reaction led Northern Power Grid to consider professional radio. Fixed point to point, low power radio could deliver an advantage over copper: since there would be no cabling, there could be no theft.

Northern Power Grid turned to professional radio specialists Wood & Douglas which has replicated the copper line protection using its ScanLink telemetry radio. It uses ScanLink to generate an audio protection signal over analogue voice frequencies. Should a power line be compromised, the radio link instantly signals the substation to switch out the line.

For power suppliers like Northern Power Grid, it is critical that protection systems are duplicated - usually with product from two different manufacturers – to ensure the entire application is not vulnerable to an endemic failure in a product family. Wood & Douglas also created a second, entirely digital solution, deploying its Sentinel digital radio systems.

Sentinel digital radios are designed for data transmission applications within Supervisory Control and Data Acquisition (SCADA) systems, supporting both Point-To-Point and Point-To-Multipoint operation, which makes the radios perfectly adapted for the future needs of power companies wishing to ensure tele protection of the power grid. Sentinel’s low latency digital radio modulation allows easy pairing with the latest generation of digital protection relays made by the major switch gear manufacturers. It gives rapid transmit and receive turnaround time which is so critical in monitoring power fluctuations.

This flexibility is increasingly important to power companies such as Northern Power Grid as they work with private wind and solar farms selling energy to the grid. These additional new power supplies must be able to feed energy in a controlled manner into a substation, and radio telemetry provides the necessary monitoring to ensure connections are immediately tripped if there is a problem isolating feeds to the grid via protection relays.

  • High speed radio link protects national grid installations
  • Low cost alternative to cabling reduces threat of theft
  • Distinct analogue and digital radio telemetry solutions address issues of endemic failure

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