Retrofilling transformers for safety in the UAE

CASE STUDY OVERVIEW

Customer: Sharjah Electricity and Water Authority (SEWA)
Location: Sharjah Gold Souk, UAE
Date: 2009

Application: Distribution Transformer, Retrofilling
Highest Voltage: 11kV
Rating: 1.5MVA

Featured Products: Midel 7131

High risk transformers in public places

SEWA had a number of distribution transformers which had been identified as high risk because they were mineral oil filled, located in public places and run at high temperatures. The mineral oil within these transformers represented a fire hazard because it typically has a low fire point of 170°C. If there had been an electrical fault in one of these transformers which ruptures the tank, it was possible there would have been a major fire incident.

Representatives from M&I Materials travelled to Sharjah to discuss the possibility of using MIDEL 7131 in these high risk transformers, in order to significantly reduce the fire hazard. The meetings were well received and a distribution transformer located within a gold souk was chosen to use as a pilot project. This particular unit was very heavily loaded and the temperature gauge showed maximum temperatures of 118°C had been reached in service.

Step by step retrofill instructions

M&I Materials provided the customer with a comprehensive guide to retrofilling mineral oil with MIDEL 7131. This included step by step instructions for a successful outcome. The content of this guide was discussed with the customer at length to ensure it was fully understood. M&I Materials also provided some guidance on pre-retrofill testing to assess the condition of the transformer; this was mainly based on the furan results.

Two members of the Midel team attended the retrofill to advise the customer’s engineers and ensure that it proceeded to plan. In order to minimise disruption to customers within the gold souk work commenced at around 23:00, with the aim of completing before the start of business the following morning. This was a shorter duration than is normally recommended by M&I Materials but the process was carefully monitored. The retrofill was completed and the transformer was energised by 08:00 in the morning, ready for the opening of the gold souk.

Greater fire safety

Following the retrofill, samples of the oil in the transformer have been analysed by the M&I laboratory and demonstrate that the fire point of the oil in the transformer is now substantially higher, which has significantly increased the fire safety of the installation.