Latest / Silent Sentinels- Protective Relays for A-C and D-C Systems / 007 - Automatic Control

Transcript

007 - Automatic Control · Silent Sentinels- Protective Relays for A-C and D-C Systems

• 0:01
  Speaker 1: Chapter five of Silent Sentinels by Westinghouse Electric and Manufacturing Company.
• 0:10
  Speaker 1: This LibriVox recording is in the public domain. Automatic control substations,
• 0:20
  Speaker 1: depending on the method used in their operation, may be
• 0:25
  Speaker 1: divided into three classes, manual, semi automatic, and automatic. Regardless
• 0:32
  Speaker 1: of its type, a station must be a highly reliable
• 0:36
  Speaker 1: source of power supply. The necessary operations in a substation
• 0:43
  Speaker 1: which serves the purpose of transforming alternating current into direct
• 0:48
  Speaker 1: current by means of synchronous converters or motor generators are
• 0:53
  Speaker 1: therefore the starting and stopping of such machines when the
• 0:57
  Speaker 1: system demands it, and the provision of adequate protection against
• 1:02
  Speaker 1: faulty action, either in case of some trouble out on
• 1:06
  Speaker 1: the system or in case of trouble within the substation equipment.
• 1:11
  Speaker 1: The automatic substation today is more dependable than is the
• 1:16
  Speaker 1: manually operated station. The design and development of relays with
• 1:22
  Speaker 1: a high degree of accuracy, sensitivity, and reliability have made
• 1:28
  Speaker 1: such an automatic substation a possibility. The characteristics of the
• 1:34
  Speaker 1: automatic substation, which must be supplied by adequate relays, might
• 1:40
  Speaker 1: be roughly divided into two classes, namely control and protection.
• 1:47
  Speaker 1: The control methods consist in the automatic starting of one
• 1:51
  Speaker 1: or more of the machines in the station. This may
• 1:55
  Speaker 1: be introduced in any one of several ways, depending on
• 1:59
  Speaker 1: the conditions to be met, and is generally accomplished through
• 2:04
  Speaker 1: some form of remote control or by means of a
• 2:08
  Speaker 1: voltage relay which closes its contacts at some predetermined value
• 2:14
  Speaker 1: of reduced line voltage. Starting due to momentary drop in
• 2:20
  Speaker 1: voltage or when the alternating current voltage conditions are incorrect
• 2:25
  Speaker 1: is prevented by an induction type alternating current voltage relay.
• 2:31
  Speaker 1: While many of the operations are common to both synchronous
• 2:36
  Speaker 1: converters and motor generators, the following outline of system is
• 2:41
  Speaker 1: especially applicable to synchronous converters. When conditions are favorable for starting,
• 2:50
  Speaker 1: a sequence of relay actions serves to perform the necessary
• 2:54
  Speaker 1: functions such as lifting the converter brushes, connecting the converter
• 3:00
  Speaker 1: to the starting tap of the power transformers, and other
• 3:04
  Speaker 1: operations depending on the type of substation. After the converter
• 3:09
  Speaker 1: has started to rotate. Synchronism and polarity are indicated by
• 3:14
  Speaker 1: a polarized motor relay, which, in case of reversed polarity,
• 3:19
  Speaker 1: causes the polarity of the machine to be corrected by
• 3:23
  Speaker 1: reversing the field. The armature of the relay motor is
• 3:28
  Speaker 1: connected to the converter pilot brushes, and during the period
• 3:33
  Speaker 1: of starting, the polarity of the relay becomes that of
• 3:36
  Speaker 1: the machine. As the converter comes up to synchronous speed,
• 3:41
  Speaker 1: alternating current of diminishing frequency flows through the motor armature
• 3:47
  Speaker 1: until synchronism is reached without causing rotation. At that time,
• 3:53
  Speaker 1: the armature will revolve in drive a drum switch in
• 3:56
  Speaker 1: the direction corresponding to the converter pole. If the polarity
• 4:02
  Speaker 1: is incorrect, the drum switch causes the field connection to
• 4:06
  Speaker 1: reverse by means of a double throw contactor switch. The
• 4:10
  Speaker 1: reversed connection is maintained only long enough for the voltage
• 4:15
  Speaker 1: default to zero and then to release the controlling relay,
• 4:19
  Speaker 1: which causes the normal field connection to be re established.
• 4:24
  Speaker 1: By this operation, the converter has been caused to slip
• 4:29
  Speaker 1: a pull and thus correct the polarity. The polarized motor
• 4:34
  Speaker 1: relay continues to operate and causes a transfer relay to function.
• 4:40
  Speaker 1: This relay in turn opens the starting contactor, causing operation
• 4:46
  Speaker 1: of the direct current brush operating mechanism. Which lowers the
• 4:50
  Speaker 1: brushes to the commutator. At this time, the main direct
• 4:55
  Speaker 1: current switches are closed and the machine is connected to
• 4:58
  Speaker 1: the load. The final function of the control part of
• 5:02
  Speaker 1: the substation equipment is to disconnect the machine from service.
• 5:08
  Speaker 1: This operation is introduced by the action of a sequence
• 5:11
  Speaker 1: of light load control relays. Protective equipment is provided not
• 5:17
  Speaker 1: only in the automatic substations, but also in the manually
• 5:22
  Speaker 1: operated or the semi automatic stations. It is provided by
• 5:26
  Speaker 1: induction type single and polyphase relays, which prevent the station
• 5:31
  Speaker 1: from starting under abnormal conditions of alternating current line voltage,
• 5:36
  Speaker 1: such as low voltage, open phase or reverse phase. The
• 5:41
  Speaker 1: same type of relay causes the station to shut down
• 5:45
  Speaker 1: on unbalanced phase conditions. If the trouble is within the station,
• 5:50
  Speaker 1: a lock out relay prevents restarting, and if the unbalanced
• 5:54
  Speaker 1: phase condition is outside the station, the automatic equipment functions
• 5:59
  Speaker 1: to the apparatus into service as soon as the line
• 6:03
  Speaker 1: is restored to normal. Each bearing is equipped with a thermostat, which,
• 6:09
  Speaker 1: in case of a hot bearing, locks the machine out
• 6:12
  Speaker 1: of service until the contexts of the thermostat device has
• 6:16
  Speaker 1: been reset by hand. A thermal relay also protects the
• 6:21
  Speaker 1: winding of the machine from overheating due to continued overload.
• 6:26
  Speaker 1: Other protective devices are the direct current directional relay, an
• 6:31
  Speaker 1: overspeed device, an inductive type alternating current overload relay, a
• 6:37
  Speaker 1: thermostat preventing overheating of the current limiting resistors, and a
• 6:42
  Speaker 1: lockout relay which locks the equipment out of service in
• 6:46
  Speaker 1: case of failure of any part of the apparatus. The
• 6:50
  Speaker 1: protection of the equipment is complete and responds immediately in
• 6:55
  Speaker 1: case of trouble, thus eliminating the losses which often occur
• 6:59
  Speaker 1: in man only operated substations because of the vary impossibility
• 7:04
  Speaker 1: of handling an emergency in the required time or the
• 7:08
  Speaker 1: inability of the operator to do so. In addition to
• 7:13
  Speaker 1: this automatic operation of the substation, a number of automatic
• 7:18
  Speaker 1: selective relay equipments are in use for automatically cutting out
• 7:23
  Speaker 1: a short circuited line, or for automatically reclosing and other
• 7:28
  Speaker 1: types of necessary feeder operation. It can be seen from
• 7:33
  Speaker 1: this description what a large part the relays play and
• 7:36
  Speaker 1: automatic substation equipment, and also how absolutely necessary it is
• 7:42
  Speaker 1: to have relays which are not only highly reliable and
• 7:46
  Speaker 1: accurate at the time of their installation, but also which
• 7:51
  Speaker 1: will maintain this high degree of accuracy and reliability throughout
• 7:56
  Speaker 1: continued service. Thus, success of the Westinghill Automatic substations and
• 8:02
  Speaker 1: past experience have proved the induction types of relays, first
• 8:08
  Speaker 1: developed and manufactured by the Westinghouse Company, to be especially
• 8:12
  Speaker 1: suitable for this type of service. By the use of
• 8:16
  Speaker 1: the induction type relays, precision of operation is not only assured,
• 8:22
  Speaker 1: but the exact calibration can be maintained throughout a long
• 8:26
  Speaker 1: period of operation. Thus, the induction relay has solved many
• 8:31
  Speaker 1: of the difficulties which were formally experienced when plunger type
• 8:36
  Speaker 1: relays had to be depended on for various functions. Most
• 8:41
  Speaker 1: of the relays supplied with the present day automatic substation
• 8:46
  Speaker 1: equipment are standard protective relays, as described elsewhere in this publication.
• 8:52
  Speaker 1: In some cases it is necessary to somewhat modify the
• 8:57
  Speaker 1: characteristics of the relay, but the fundamental principles of design
• 9:02
  Speaker 1: and operation are maintained. The CV voltage relay is used
• 9:07
  Speaker 1: throughout as a timing voltage relay to provide a definite
• 9:12
  Speaker 1: time delay where necessary. A slight modification of this relay
• 9:17
  Speaker 1: consists in having the contacts geared to the disc shaft
• 9:21
  Speaker 1: rather than mounted directly on it, which provides a relay
• 9:26
  Speaker 1: with a much longer time delay characteristic than the standard.
• 9:30
  Speaker 1: The GK time delay relay, also used largely in automatic
• 9:35
  Speaker 1: substation equipment, is motor operated and is highly reliable. A
• 9:41
  Speaker 1: recent addition to the relay family is the MF flash relay,
• 9:46
  Speaker 1: which is used in automatic substation protection to disconnect the
• 9:51
  Speaker 1: rotary in case of a flashover occurring between the commutator
• 9:55
  Speaker 1: and the frame and of Chapter five five