Electrical System

monitoring electrical consumption

monitoring electrical consumption

Electrical power is the most widely used of all the power in buildings. It is distributed from the Electrical Utility Board. In this section, we will only look at the distribution of electricity once it has arrived at the consumer’s buildings, the processing of it, the protection of equipment and many others.

For most heavy users of electricity, the incoming voltages of the electricity are 11 KV or 33 KV. The voltages are made to be high so that heat losses is minimized and efficiency is improved. At the user end, most of the machines use very much lower voltages, in the region of 380 V to 500 V. There must be a way to reduce the incoming voltages in order to be useful.

Step-down transformers are used to reduce the voltages without substantial losses. Once the voltages are stepped down, it is channeled into switchboards with isolator switches for distribution to any area.

high voltage oil immersed power transformer

high voltage oil immersed power transformer

For safety purposes, it is required that isolator switches be installed to cut off the power supply anytime required. For the high voltages, special switchgears have to be installed to take into consideration the possibility of sparking that can lead to dangerous explosions. This is covered in the section on HV Switchboards. Switchgears for LV need not be so stringent. They are covered in the section on LV.

The wiring to distribute the electrical current is chosen based on certain minimum requirement of suitability. Underground cables, cables for essential services like elevators, cables for control, cables for high voltages, will be covered in another section on wiring.

high voltage switch gear racked out for servicing

high voltage switch gear racked out for servicing

Power conditioning equipment is used to enable the most efficient use of the electricity supplied. Capacitor banks are used to reduce power factor. Smoothening circuits are sometimes used for critical measuring equipment to reduce error. Uninterruptible Power Supply or UPS is used to provide power in times of failure of the Utility Board. The use of inverters to provide variable voltages for speed control of motors is quite common in energy efficient buildings.

motor driving a chilled water pump for air conditioning system

motor driving a chilled water pump for air conditioning system

Motors of all sizes are the prime movers of machines. They have special requirement. Big motors draw very high currents during starting. Special motor starter boards are designed to enable motors to start and run safely. Protection circuits and devices are installed to protect electrical equipment, wiring, and the people handling them. Sometimes control equipment is incorporated into motor starters for automation.

totally enclosed motor in a canned pump

totally enclosed motor in a canned pump

Different types of motors are currently being used. The most common squirrel cage induction motor is found where the speed is constant. Wound-rotor or DC motors are used when speed control is required. Single-phase motors require capacitors or additional coils to start.

Weatherproof construction, explosion proof for flammable areas, insulation class for windings, and similar topics are also included in the topic on Electrical Systems.