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Coex Training

Current Transformers

Current transformers normally have a single conductor as a primary winding connected in the run of the line conductors. The voltage which appears across the primary terminals is very small and therefore the voltage at…

Understanding Voltage & Current

In most types of electrical equipment, the current in a circuit is proportional to the voltage across that circuit. For example: If a voltage across a circuit is lowered, then the current flowing in that…

Switching Programs Terminology & Abbreviations

Before starting to write a switching program, it is important to understand and use standard terminology. The table below includes some common fields found on templates.   Program Field Meaning Program number This is obtained…

Switching Programs & Switching Operations

High voltage switching is a high-risk task, and as such the use of switching programs is critical. A switching program is a written list of sequential logical operations to permit isolation and re-energisation of electrical…

Ring Main Units

Ring main units (RMU) are widely used in industry and for distribution systems. RMUs operate independently, which means that it is possible to earth an incoming supply cable while it is still energised from the…

Power & Distribution Transformers

The standard power transformer is “on-load tap changing” (OLTC) to ensure that the secondary distribution voltage is within limits although the primary voltage may change. Tap changer range is usually from 15% above normal to…

Voltage Transformers

Voltage transformers on the other hand carry full system voltage but no significant current.  They have a fine wire of many turns on the primary winding (very high resistance and inductance) connected between the phase…