8. The technology developed by them is under consideration.
18 20
Home exercise. Read the text. Make up a plan and be prepared to retell it.
Power Plant Control System Operation of Central Unit
Adjustable level detectors determine at which busbar load a generator shall start or stop. According to the starting sequence, selected with push-buttons at the front, start and stop orders are distributed to the basic units. These orders are delayed one minute in order to prevent actions by temporary load variations. The delay will be bypassed when a fault occurs on a running set, overload is detected or a controlled load is required.
The unit also determines whether or not the number of connected sets is sufficient to cover the required load under normal conditions. In this case a signal to the units will permit a set with a non-critical fault to be disconnected and stopped. This signal will also permit a requested controlled load to be connected.
The unit provides the heavy load control function. When a controlled load is requested by an external closing contact, a simulated load will be added to the real load and this may result in the starting of a new set. When enough power is available, permission will be given to connect. Eight loads can be controlled, programmable from 20% to 160% of a generator capacity. The connection order is given at 2 s intervals for each 1 pad. After black-out a delay of 30 s will prevent the connection of these loads from interfering with the connection of essential consumers.
At the request of a controlled load a corresponding lamp at the front starts flashing until the load is ordered to be connected and then it changes to steady light. The lamp remains lit and the control output activated until the request contact is opened.
Hometask: Ex. 10, 15, 17, 18.
The third class period
19 4
Listen to the text about operation of internal monitoring of power plant control system. Give it free translation.
A speciality of the system is the internal monitoring feature which indicates abnormal conditions such as interruption, earth fault or malfunction of certain connected devices.
An internal failure will be indicated by the lamp of the unit containing the detection circuits for that particular fault. Further indication is given by light emitting diodes, visible when the front plate is removed.
The basic unit and the additional monitoring unit each have one contact, opening at internal alarm state. Synchronizing/load sharing unit and relay unit are connected to the basic unit in order to affect this contact.