Electrical4U 
High Voltage Test (Water Immersion Test) :Type, acceptance and routine tests are the three factory groups. For the water-immersion type test, IS 1554-1 takes about 3 m of core from the finished cable or cord. The core sits in a water bath with the ends at least 200 mm above the water. General-purpose PVC uses … Read more
A power cable is sized and rated for voltage, continuous current, short-circuit current and voltage drop. Overhead lines or buried circuits can both carry the same load. Power cables are the sheathed assemblies used for power transmission and distribution. Each core is one or more individually insulated electrical conductors, usually held together with an overall … Read more
In an electrical or electronic plant an Annunciator is a panel that announces a fault or an unusual process state so the operator can see which point has gone abnormal. What is Alarm Annunciator? An alarm annunciator is an audio-visual warning. A window flashes and a horn sounds when a field contact changes state. The … Read more
Loss of field or excitation means the field supply has failed. On a large machine that supply is often a separate auxiliary source or a separately driven DC generator. If that auxiliary supply or its driving motor fails, the machine loses field. After loss of excitation it runs above synchronous speed.The generator or alternator then … Read more
Stator earth-fault protection limits earth current when a stator winding of an alternator goes to earth. The stator star point is earthed through an impedance so the current is small enough to limit burning of the core and winding. If that impedance is high, earth current can sit below rated current. Phase differential relays then … Read more
Rotor earth-fault protection watches the field winding of an alternator for a connection to earth. One earth fault on an otherwise isolated field does not circulate current. A second earth fault shorts part of the winding, unbalances the air-gap magnetic field and can damage the bearings. Find the first field earth fault and take the … Read more
An inter-turn stator fault shorts two turns of the same phase in one slot. Longitudinal differential and stator earth fault protection often miss it until the puncture reaches another phase or earth. A dedicated scheme is used on machines with many conductors of different potential in the same slot. The fault often becomes an earth … Read more
A generator needs protection because insulation stress, mechanical force and temperature rise can destroy the machine. Those forces act on every alternator in service. A machine that stays within rating still sees brief overloads. Protection must still clear a fault before that overload becomes a winding or rotor failure. Relays and mechanical trips limit overload … Read more
Electrolyte of Lead Acid Battery Care of a flooded lead acid battery cell means keeping electrolyte strength, cell voltage and water level within the maker’s limits so the plates stay as lead dioxide and sponge lead. The electrolyte is sulfuric acid in distilled water. Concentrated sulfuric acid has a specific gravity of about 1.84. Stationary … Read more
In power system protection a differential relay is the usual unit scheme for protecting transformers and generators from faults inside a defined zone.Differential relays trip when the difference between two or more similar currents or voltages exceeds a set value. They stay stable for a fault outside that zone. An over current relay trips when … Read more