Electrical Substation

1. INTRODUCTION Electrical substation for distribution system is the main supply to convert the high voltage (HV) to low voltage (LV) and the place where load are distributed to the consumers. In Malaysia, Tenaga Nasional Berhad Distribution (TNBD) used the 33/0. 433kV, 22/0. 433kV, 11/0. 433kV and 6. 6/0. 433kV voltage system for the electrical system to supply for domestic consumer and industrial consumer such as factory which will supplied directly from Transmission Main Intakes (PMU), Main Distribution Sub –station (PPU) or Main Switch Sub – station (SSU).Electrical substation is the place where all electrical equipments such as high voltage switching, three phase transformer, high voltage cables, low voltage cables, low voltage feeder pillar, battery charging and etc which are used for electrical supplying in power system and to make sure the safety of the system by the protection scheme. Basically, electrical system have one or several in coming and out going circ uit which are controlled by high voltage switching and meet in one or more in the same of busbar system.Generally, electrical substation is a point in distribution system where: * A place where several electrical equipments are installed and used for electrical energy in power system. * A place where the safety of the system is provides by automatically protection scheme. * A place where one or several incoming and outgoing circuit are met at one or more busbar system and controlled by high voltage switching equipment which is used for switching. * A place where voltage value is changed and controlled. A place where load are distributed, controlled and protected FUNCTIONS OF A SUBSTATION * Supply of required electrical power. * Maximum possible coverage of the supply network. * Maximum security of supply. * Shortest possible fault-duration. * Optimum efficiency of plants and the network. 2. OPERATION OF 11 kV MODULAR POWER PLAN LAB Electric power is normally generated at 11-25kV in a power station. To transmit over long distances, it is then stepped-up to 400kV, 220kV or 132kV as necessary. Power is carried through a transmission network of high voltage lines.Usually, these lines run into hundreds of kilometres and deliver the power into a common power pool called the grid. The grid is connected to load centres (cities) through a sub-transmission network of normally 33kV (or sometimes 66kV) lines. These lines terminate into a 33kV (or 66kV) substation, where the voltage is stepped-down to 11kV for power distribution to load points through a distribution network of lines at 11kV and lower. The stepped-down voltage of 11kV is channelled to the RMU(Ring Main Unit) and outgoing feeder of the substation.This is to ensure the continous supply of electricity even during maintenance. The RMU unit is speacially designed that during maintence the affected users will receive supply from a different substation which is interconnected. This is because maintenance have to b e carried out in an ON condition. 3. BLOCK DIAGRAM OF 11kV MODULAR POWER PLAN 4. FUNCTIONS AND MAINTAINENCE OF ALL EQUIPMENTS 5. 1 Switch gear/ circuit breaker In an  electric power system,  switchgear  is the combination of electrical disconnect switches,  fuses  or  circuit breakers  used to control, protect and isolate electrical equipment.Switchgear is used both to de-energize equipment to allow work to be done and to clear  faults  downstream. This type of equipment is important because it is directly linked to the reliability of the  electricity supply. Typically, the switchgear in  substations  is located on both the high voltage and the low voltage side of large power  transformers. The switchgear on the low voltage side of the transformers may be located in a building, with medium-voltage circuit breakers for distribution circuits, along with metering, control, and protection equipment.For industrial applications, a  transformer  and switchgear line-up may be combined in one housing, called a unitized  substation  or USS. Types of circuit breakers: I. Oil Oil circuit breakers rely upon vaporization of some of the oil to blast a jet of oil through the arc. II. Gas Gas (SF6) circuit breakers sometimes stretch the arc using a magnetic field, and then rely upon the dielectric strength of the SF6  to quench the stretched arc. III. Vacuum Vacuum circuit breakers have minimal arcing (as there is nothing to ionize other than the contact material), so the arc quenches when it is stretched to a very small amount (