Distribution Transformers

The purpose of a distribution transformer is to reduce the primary voltage of the electric distribution system to the utilization voltage serving the customer.

A distribution transformer is a static device constructed with two or more windings used to transfer alternating current electric power by electromagnetic induction from one circuit to another at the same frequency but with different values of voltage and current.

Earth Fault Indicator (EFI)

The picture shown tells how this device works.

Earth Fault Indicator (EFI) is a part of a distribution network that is provided for each of the incoming cables in a ring circuit to indicate the faulty section during earth fault.

EFI is composed of an earth fault relay and indicator which is directly operated by a secondary current from the split-core type core-balance transformer. The indicator is automatically re-set by single phase 230V supply.

Commissioning of 150MVA, 132/11kV DLFF Substation

I had the privilege to be part of the commissioning team for one of the substations of Dubai Electricity and Water Authority (DEWA), namely Dubai Logistics Freight Forwarders or DLFF 132/11kV, 3x50MVA Substation. This means that now, the electrical energy for the whole city of Dubai has again increased.

The team composed of the Commissioning Engineer, Protection Engineer, Transmission Operator, SIEMENS contractor, and yours truly from the Distribution System Operation.

The scope included commissioning of gas-insulated switchgear (GIS) by SIEMENS; 2×132kV line feeder; 3×50MVA inter-distribution transformer feeder; and a double busbar including bus-section disconnectors and earthing switches; automation system is used for control and monitoring. The man-machine interface is the BAILEY SCADA by ABB.

The Ring Main Unit (RMU)

In my work as an Assistant Engineer, Distribution Operation here at Dubai Electricity and Water Authority, I always meet this robot look-a-like machine. But it's not a robot, it's called RMU.

The Ring Main Unit (RMU) is a type of switchgear used in the distribution networks that is normally formed by interconnecting a number of ring shaped grids. It is designed to operate at the rated nominal system voltage of 11kV and is normally consist of switches on both sides of the T-off, one to open the ring and another at the connection to the distribution transformer (usually rated 1000kVA) using one of the following:

    Swith and fuse separately
    Switch-fuse combination
    Circuit breaker