remote control equipment - Indian Railways Institute of Electrical ...

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e frequently resynchronised by dividing the message into short blocks of characters, each with their own synchronisation bits. This is advantageous where short messages with quick synchronisation is desired. Thus, the efficiency is relatively high. The asynchronous modem is limited to 1800 bps in most applications and is usually of the FSK type. Cost is very low. The synchronous modem on the other hand transmits a synchronising clock signal alongwith the data, so that the receiver is precisely synchronised with the transmitor. This permits very long message and high data rates without any problem of falling out of sync. Sync. modems are generally available from 2400 bps to 1 Mbps and are higher in cost. 7.2.5.2 Communication message formats The transmission of information between master and remote using TDM techniques requires the use of serial digital messges. These message must be efficient, secure, flexible and easily inplemented in hardware and software. Efficiency is defined as - Infromation bits transmitted/total bits transmitted. Security is the ability to detect errors in the original information transmitted, caused by noise on the channel. Flexibility allows different amounts and types of information to be transmitted upon command by the master station. Implementation in hardware and software requires the minimum uncomplicated logic, memory, storage, and speed of operation. 7.2.5.3 All message are divided into three parts as follows * Message establishment, providing the signals for the receiver to select the message transmitted to it at the correct time, from hundreds of other possible messages and channel noise. * Information, which provides the data to be sent to the receiver, in coded form to allow the receiver to decode the information and properly utilise it. * Message termination, which provides the message security checks so that no errors in the message establishment of information fields are accepted by the receiver and provides a mean of denoting the end of the message. Message security checks consists of logical operations on the data which results in a pre-defined number of check bits transmitted with the message. At the reveicer end the same operation are performed on the data and compared with the received check bits. If they are identical, the message is accepted; otherwise, a retransmission of the original message is requested. 129
A typical example of commonly used asynchronous message format is shown below : 8 msec pre Tx mark S M 2 bits 4 bits 8 bits 12 bits 5 bits 1 bit RTU Address Fund Code 130 BCH Sec Code Synchronisation End of message (Message Establishment) (Information) (Message Termination) The Message Establishment field has three components : • 8 mesc min. pretransmission mark to condition modern receiver for syncbits. • Synchronisation, which consists of two bits, a space followed by a mark. M Add. Mess age RTU address, which allows a receiver to select the message addressed to it from the message to all the RTUs on a party-line. The information field contains 20 bits, of which 8 bits are function code and 12 bits are used for data. For remote to master message, this represents the first message in the sequence; additional messages directly following the first message also transmit information in the RTU address and function code spaces, so that 24 of data are transmitted. These 24 bits may contain two 12 bit analog values or 24 bits 24 device status. 7.2.5.4The message termination field contains • BCH security code, which has 5 bits and allows the receiving logic to detect most message errors. If an error is detected, the message may then be retransmitted to obtain a correct message. • End of message mark, which provides the last bit as a mark, so that another message can follow immediately after this message. 7.2.6 INFORMATION TRANSFER 7.2.6.1 Master to remote data transfer : Information transmitted from master to remote is for the purpose of device control, set point control, or batch data transfer. Due to the possible severe consequences of operating the wrong device or receiving a bad control message, additional secruity is required for control, this is provided in the form of a sequence of messages, commonly called select before operate sequence, as shown below :-
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PREFACE The book on "Power Supply I
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However transformers of capacity 13
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3. To keep the unbalance on the 3 p
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1.2 POWER SUPPLY FOR SIGNALLING 1.2
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locomotives and Electric Multiple U
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2.0 Supply System 2. POWER SUPPLY F
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figures. This charge should be real
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2.4 Scrutiny of Bills have a bearin
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c) Procedure to be followed in case
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In the territorial setup one Subord
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3.2.3 Over load Capacity of Tractio
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B. Insulation resistance will conti
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3.3. GUIDING NOTES ON MAINTENANCE 3
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f) Fully push home the wedges betwe
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eakers/interrupters should also be
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A detail history of every battery s
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light or bluish grey according to a
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(e) Overhaul, bench tests and calib
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3.5. FORTNIGHTLY MAINTENANCE 3.5.1.
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obstruction and also if the shock a
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2. Test a sample of oil for BDV. 3.
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3. Check if the terminations of the
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Fortnightly Schedule: a) Drain wate
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d) Measure the IR between auxiliary
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TRACTION DISTRIBUTION SCHEDULE OF M
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3.0 Inspection of Traction Sub-stat
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4.0 Switching Stations a) Switch Ya
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SI. No . APPLICATION AND INTERPRETA
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2.2 Oxidation Carbondioxide is the
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3.4 Pattern of generation of gases
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TABLE - I SOLUBILITY OF DIFFERENT G
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TABLE V ROGER'S METHOD OF DIAGNOSIS
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1.1 Schedules MAINTENANCE OF SF6 CI
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Point / Location Tripping Mechanism
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1.0 General Annexure 3.05 MAINTENAC
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1.5 Detailed Check Checking shall b
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DESIGN ASPECTS OF TRACTION SUBSTATI
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• Characteristics of the locomoti
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considerations enlisted in para 4.0
Page 81 and 82: xii) Load losses 135.0 kW xiii) Cur
Page 83 and 84: item Nominal System Voltage 66kV 11
Page 85 and 86: 20 1250 1600 2000 245 31.5 1250 160
Page 87 and 88: i) Three post, centre post rotating
Page 89 and 90: etween live parts and different pot
Page 91 and 92: 4.11.5 Design of grounding system 4
Page 93 and 94: 4.12.2 BIL of various equipments us
Page 95 and 96: (d) High speed inter tripping relay
Page 97 and 98: The relay continuously monitors the
Page 99 and 100: SULFUR HEXAFLUORIDE(SF6) GAS 96 ANN
Page 101 and 102: 5.0 POWER SUPPLY SYSTEM PROTECTION
Page 103 and 104: any one of the two sub-staion throu
Page 105 and 106: fault relay (132KV&25KV side) 4. ID
Page 107 and 108: will be supplied to the successful
Page 109 and 110: detected by normal distance protect
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Page 125 and 126: Just as the requirements of supervi
Page 127 and 128: The use of hermetically sealed comp
Page 129 and 130: The configuration used in Railway S
Page 131: This may be accomplished by several
Page 135 and 136: 7.2.6.2The above sequence of messag
Page 137 and 138: 7.3 SCADA EQUIPMENT 7.3.1 General T
Page 139 and 140: 7.3.10 SCADA Software The operating
Page 141 and 142: systems are different, the basic fe
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Page 145 and 146: To combat interference, co-ordinate
Page 147 and 148: e = Er / R were introduced in the v
Page 149 and 150: It is seen that even if the lines a
Page 151 and 152: Fig. 8.3 Fig. 8.3 contains a family
Page 153 and 154: Typical Rail Current Distribution F
Page 155 and 156: 8.8 SUPPRESSION OF INTERFERENCE AT
Page 157 and 158: Magnetizing current is required to
Page 159 and 160: REGULATION FOR ELECTRICAL CROSSING
Page 161 and 162: Kc is cable screening factor and it
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