Thursday, 19 January 2017

OBJECTIVES OF POWER SYSTEM - ELECTRICAL POWER SYSTEM

The objective of power system control is to maintained continuous electric supply of acceptable quality by taking suitable measures against the various disturbances that occur in the system.
These disturbances can be classified into two major heads, namely, small-scale disturbances and large scale disturbances.

OBJECTIVES


Small Scale Disturbances

Small scale disturbances comprise slowly varying small magnitude changes occurring in the active and reactive demands of the system.
The small scale disturbances can be overcome by regulating controls using  governors and exciter.


Large Scale Disturbances

The large scale disturbances can only be overcome by proper planning and adopting emergency switching control.
Large scale disturbances are sudden large magnitude changes in system operating conditions such as faults on transmission network, tripping of a large generating unit or sudden connection or removal of large blocks of demand.


Objectives of Power system control

To meet continually changing load demand
Adequate “spinning” power reserve
Minimum cost of energy
Minimum environmental pollution


The “quality” of power supply
                (a) constancy of frequency
                (b) constancy of voltage; and
                    (c) level of reliability

Frequency Regulation
System frequency, must remain within its operational range
                         f min < f(t)  <  f max
                      49.5 Hz < f(t)  <  50.5 Hz

Voltage Regulation
Bus voltages must remain within their operational limits
                         V min < V(t)  < V max
                      0.95 pu < V(t)  < 1.05 pu


Quality is normally described by means of an accepted voltages profile (level and amount of flicker) and frequency (set point with a narrow band and a threshold for the time delay) of the delivered electric power.

Security is much more difficult to describe in quantitative terms. There are normally certain rules in utilities and power pools concerning power system balance, network operation etc. In order to successfully take care of care of some predefined disturbances.


Economy consists of two parts: The investment part of apparatus, control system and so on, and the running cost for the while power system.

To keep the objectives on reasonable level it is a must today to take advanced control systems into service.

0 comments:

Post a Comment