Short Circuit Current Calculations for Symmetrical and Unsymmetrical faults
Short Circuit Current Calculations for Symmetrical and Unsymmetrical faultsIt is not practical to design a power system which is free from failure. Hence we need to design the system which is capable of withstanding the faults till the fault is cleared by circuit breakers. It is necessary to select the circuit breaker which has the capability to interrupt the worst case fault curre [...]
Methods Of Reducing short circuit current
METHODS OF REDUCING SHORT CIRCUIT CURRENT An electrical circuit in which a very low resistance path has been accidently opened. When the resistance in a circuit decreases the current in the circuit increases drastically, which can damage the circuit and cause fires. As a result, we have used certain equipment and other concepts in order to reduce the short circuit current. Increasi [...]
CONTINGENCY ANALYSIS
CONTINGENCY ANALYSIS Contingency analysis is most important part of Power system study to assess the capability of the power system to meet the load without violating voltage and equipment loading limits. It is impractical to design a power system which is free from failures. Faults in the system have to be isolated quickly so that the rest of the system functions without disturba [...]
Short Circuit Calculation – Symmetrical and Asymmetrical Fault Current
Short Circuit Calculation In this model, grid is modelled with short circuit current of 40kA and X/R ratio of 14, two winding transformer rating of 100 MVA, 220/33kV, %Z is 8.35 and X/R is 13. Fault is created at bus 2, the calculations for symmetrical RMS current is made below. Impedance Correction Factor: Transformer Impedance: Grid Impedance: Three Phase Fault: Manual Calculatio [...]
LV Coordination
Protection in Low Voltage Systems: Voltage between 50V and 1000V AC is considered low voltage. The short circuit current varies in Low Voltage and High Voltage systems. The fault current is largely determined by the impedance of the fault. In the LV system, the impact is thermal only with a higher short time rating is about 1 to 3 seconds. The LV Protective Devices: Based on the o [...]
Transformer Protection – Over Current and Earth Fault
Transformer Protection - Over Current and Earth Fault Transformer Protection: Transformer Protection - Transformers are static devices, totally enclosed and generally oil immersed. Therefore, chances of faults occurring on them are very rare. However, the consequences of even a rare fault may be very serious unless the transformer is quickly disconnected from the system. This nece [...]
Motor protection using fuse
Motor protection using fuse Network consist of 11kV grid through a 50kVA transformer, 3.7 kW motor with Fuse is connected. The motor is rated at 0.415 kV and its full load current is 7.6 A. The motor protection considered for various standard fuse ratings as follows (8A, 10A, and 16A). Case 1: Consider a 8A fuse; in this case, the motor's starting characteristics curve exceeds the [...]
Transformer X/R Ratio – Effect on Instantaneous Over Current Settings
TRANSFORMER X/R RATIO - EFFECT ON INSTANTANEOUS OVER CURRENT SETTING FOR TRANSFORMER HIGH VOLTAGE SIDE RELAY Transformer X/R ratio affects the Instantaneous over current (IOC) (ANSI code 50) setting of transformer high voltage side relay. This happens due to asymmetrical nature of the fault current at the instant when the relay interrupts the fault current. Thus understanding the [...]
GENERATOR LOAD SHARING PRINCIPLE
GENERATOR LOAD SHARING PRINCIPLE The generator load sharing principle is crucial to understand when attempting to parallel generators at any facility, including data centers and power plants. This is because different manufacturers’ load sharing controls may not be compatible and overloading or underloading each unit must be avoided for successful and efficient generator paralleli [...]
Motor Protection – Over Current and Earth Fault
Motor Protection - Over Current and Earth Fault: Motor Protection - If the motor is heavily loaded beyond its capacity, then it is said to be in a overloaded condition, in which it draws heavy current from the supply and there will be simultaneous rise in temperature of winding and deterioration of the insulation resulting in damage of winding. Hence, the motor must be protected a [...]
Manual Calculation to find out sequence impedance
Manual Calculation to find out sequence impedance for 3 phase fault Single line-ground fault, Line-line fault and I have modelled simulation & validated with DIgSILENT results. [...]
Capacitor bank sizing calculation
1.Introduction As the name implies, capacitor bank is merely a grouping of several capacitor. It may be connected in series or parallel depending upon the required rating. Increase in the number of capacitors in a bank will increase the energy storage capacity of the bank. The intent of this document is to explain about the capacitor bank sizing calculation and power factor correc [...]