choose the correct option from the following statements: iii. Ageing, temperature, weather are factors of. ( weak of protection- weak of insulation-none of them) is the most commonly used protective device in a distribution circuit. (Fuses - Circuit breaker - Relay) faults in power systems with more than 80% of the occurring faults is .............. (Temporary Faults- Permanent Faults - none of them) iv. expressed as a fraction, is the ratio between the magnitudes of the primary and the secondary current for ideal working conditions of the curren transformer. (The knee point- Current Transformer Ratio (CTR) - Over-current relay) V. ........is the most widely used over-currrent characteristics. (Definite Time - Instantaneous-Inverse Definite Minimum Time Relay) give me the choice only ( final answer )

Choose the correct answers for the following questions : 1- Device which receives a signal from the power system and determines whether conditions are "normal" or "abnormal" (measuring function) is d. Voltage Transformer c. Current Transformer b. Relay a- Circuit Breaker 2- A ……………..is an electromechanical device break a circuit automatically under fault condition. d. Voltage Transformer c. Current Transformer b. Relay a- Circuit Breaker 3- Good Protection System Should require: d. All of these. c. Adequacy b. Selectivity & Sensitivity a- Reliability & Speed 4- That which tends to close the contacts of the relay. d. All of these. c. Restrain force b- Restrain torque a- Operating force 5- The value of current or voltage below which a relay opens its contacts and comes to original position d. Non of these. c. Set level b. Drop-out level a. Pick-up level 6- What is the purpose of back up protection? d. To leave no blind spot To guard against c. failure of primary b. To increase the reach a. To increase the speed

Are the following statements true (✔) or false (X)? i- Protection relays can be classified in accordance with their construction, the incoming signal and function. ii- Fuse is the most commonly used protective device in a distribution circuit. iii- The primary protection in distance relay fast with intentional time delay. iv- The zone of the distance relay is limited by a part of the electric circuit between the current transformers (CTs), to which the relay is connected. v- Distance relay was classified as the simple relay used in power system protection. vi- Reliability of power system protection: Assurance that the protection will perform correctly. vii- Zone 1 is set to cover 120% of the line length. ix- Ferroresonace is a nonlinear problem occurred in current transformer CTs. x- Melting characteristics is one thermal characteristic of fuse. xi- Current transformer ratio is the ratio between the magnitudes of the primary and the secondary current for ideal working conditions of the CT.

uring the open circuit test of a transformer*The secondary is supplied rated KVAPrimary is supplied with no-load currentPrimary is supplied current at high voltage.Primary is supplied rated voltage

Question 2List three functions which a transformer may perform in an electrical circuit. [3 marks]A 10kVA, 50 Hz distribution transformer has 600 turns in the primary and 120 turns in thesecondary. The primary and secondary resistances are r1 = 0.2 Ω and r 2 = 0.02 Ω respectively,and the corresponding leakage reactances are Xl1 = 1.0 Ω, and Xl2 = 0.04 Ω respectively. Thesupply voltage is 1100V.Calculate(a) The equivalent impedance, resistance and reactance, referring all quantities to thehigh voltage (primary) side; [6 marks](b) The secondary terminal voltage for full load having a power factor of 0.7 lagging;Draw the phasor diagram; [7 marks](c) The regulation in (b) [4 marks]2130310310

The no-load current drawn by the transformer is usually what percent of the full-load current ? (a) 0.2 to 0.5 per cent (b) 2 to 5 per cent (c) 12 to 15 percent (