## Introduction to transformer: How it works?

### The transformer is used to convert the incoming voltage at the location to the correct voltage (for the submersible motor in case of ESP). Transformer selection is based on mainly 4 parameters:

• Power rating in KVA (Kilo Volt Amperes),
• Primary voltage,
• Secondary voltage,
• Tap arrangement.

### Power rating in KVA for three phase transformer:

The calculation of power rating in KVA for a Three Phase Transformer is based on Winding Voltage and Amperage information. The simple formula to calculate the rating of three phase transformers is:

KVA = (√3. V x I) /1000

Refer to the post titled “How to Calculate the Required KVA Rating for three Phase Transformers? ” for more details.

## Cable Armor

As per API RP11S5, cable armor is the outer covering of the cable which provides mechanical protection during installation and removal of cables. In addition to mechanical protection, the armor provides mechanical constraint against swelling and expansion of underlying elastomeric materials in case of any exposure to well fluids.

## Braids and Coverings

As per API RP11 S5, supplementary layers of materials, named: braids and coverings, are used to guarantee a specific mechanical performance characteristics. It could be either applied over the insulation or on both sides of the jacket. Braids and coverings provide additional strength and protect the underlying cable components. On the other hand, these materials increase the cable diameter and the associated cost. Furthermore, they are also susceptible to deterioration depending on well fluids and conditions.

## Cable Jackets

As per API RP11S5, cable jackets are protective coverings used to mechanically shield the insulation from the downhole environment. The jacket materials protect the insulation from mechanical abuse associated with handling. Some jacketing material may provide secondary insulation. The most used types of jackets in submersible pump cable are made of: EPDM elastomers or nitrile.

## Cable Insulation

As per API RP11S5, cable insulation isolates the electrical potential between conductors and other conducting materials. Insulation also minimizes leakage current from the conductors.

Insulation selection depends on many factors mainly related to produced fluids properties and well behavior; such as: gas type and concentration, well environment, gas to oil ratio, pressure cycling, exposure to downhole chemicals…

There are two classes of cable insulation materials used in oil and gas industry: