Ashridge Engineering

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Transformer Protection and Monitoring


Our National Grid approved range of electronic winding temperature indicators (WTI’s) provide continuous alarm based monitoring, control and protection of transformer cooling systems.

Winding Temperature Indicator
The winding is the component with the highest temperature within the transformer and is subject to the fastest temperature increase as the load increases. In order to have control of the temperature parameter within the transformer, the temperature of the winding as well as top oil, must be measured.

An indirect system is used to measure winding temperature, since it is dangerous to place a sensor close to the winding due to the high voltage. The Winding Temperature Indicator directly measures the CT current and uses the algorithms associated with IEC354 to provide accurate winding temperatures for all cooling gradients via the feedback system.

The 852Plus has been awarded National Grid approval with Type A status for unrestricted use on SuperGrid transformers at all NGC substations.

Oil Temperature Indicator
The Oil Temperature Indicator (OTI) measures the Top oil Temperature. This is a specific measurement location at the top of the transformer and the temperature data from it is used for control and protection for all transformers.