On-line operation of power system relay protection in spring of 2005 1 reference answer, Dagong1;

First, multiple choice questions

1、D 2、B 3、D 4、A 5、C

1. The following () systems are not small current grounding systems.

A. Neutral point is ungrounded

B. the neutral point is grounded through the arc suppression coil.

C. the neutral point is grounded through a resistor.

D. Neutral point is directly grounded

2. The influence of short-circuit transition resistance of unilateral power supply system on distance protection is ().

A. Expansion of protection scope

B. Narrowing the scope of protection

C. The scope of protection remains unchanged

D. Uncertainty of protection scope

3. Directional components are used in the bidirectional power supply system to improve protection ().

A. directionality

B. Reliability

C. sensitivity

D. selectivity

4. In the three-stage current protection of unilateral power supply network, the first paragraph is ().

A. Non-time current quick-break protection

B. Time-limited current quick-break protection

C. timing overcurrent protection

D. Inverse time overcurrent protection

5. In the large grounding current system, a single-phase grounding fault occurs, and the relationship between the distance between the fault point and the bus and the zero-sequence voltage value on the bus is ().

A. regardless of the location of the fault point.

B. The farther the fault point is, the higher the zero sequence voltage is.

C the farther the fault point is, the lower the zero sequence voltage is.

D. zero sequence voltage is zero.

6. In the 90 connection mode, when the line impedance angle is 60, the internal angle of the relay should be ().

A.30

B.60

C. 120

D. 150

7. Distance protection action, the relationship between the set impedance Zset and the measured impedance Zm of the protected line is ().

A.Zm & gtZset

B.Zm & ltZset

C.Zm=Zset

D.Zm≥Zset

8. The voltage-current ratio of impedance relay is () of relay.

A. measuring impedance

B. Setting the impedance

C. Action impedance

D. unable to determine

9. Make the current quick break protection has the largest protection range of operation mode for the system ().

A. Maximum operating mode

B. Minimum operating mode

C. normal operation mode

D. Accident operation mode

10. The most basic requirement of relay protection device is ().

A. Quickly

B. Selectivity

C. Reliability

D. sensitivity