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Download Type LFAA 103 Mesh Corner Unit
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Type LFAA 103 Mesh Corner Unit Features ● Automatic isolation, delayed automatic reclosure (DAR), ferroresonance suppression ● Selectable 0, 1, 2 or 3 mesh circuit breakers ● Selectable 0, 1 or 2 line disconnectors and 0, 1 or 2 transformer disconnectors ● Ferroresonance schemes F2A, F2B and F3 ● Timers are independently adjustable ● Scheme logic options can be selected ● User-friendly inbuilt keypad and menu system ● Built-in test facilities ● Scheme documentation via ladder diagram Benefits ● Wider choice of scheme logic options ● Suitable for mesh stations ● Simplified commissioning via inbuilt test feature ● Greater setting flexibility 2 Figure 1: LFAA 103 with hinged front cover open. Application Primary Circuit Description The LFAA 103 (Mesh corner unit MCU) provides for the automatic reclosure of circuit breakers, the automatic isolation of persistently faulted plant and the suppression of ferroresonance, following a fault on the system. As shown in Figure 2, the maximum circuit configuration of a mesh corner comprises three HV circuit breakers CBX, CBY and CBZ at the common node of which are two feeders and either two banked transformers feeding onto the LV busbars or two grid transformers. Each mesh breaker (CBX, CBY, CBZ) has its associated disconnectors (MXA, MXB, MYA, MYB, MZA, MZB) either side, and the feeder circuits have a disconnector (LDA, LDB) on the line side of the mesh corner. The banked transformers each have a disconnector (HDA, HDB) on the HV side and where LV busbars are being fed, an LV circuit between the transformer and the busbars. Equipment is provided on the basis of one MCU per mesh corner. Although each MCU is an autonomous unit, interunit communication guarantees co-ordinated control of a complete mesh system. A typical single switch system would require two MCUs; a two switch system, three MCUs, and three and four switch systems, four MCUs. Once the initial system has been installed (minimum two corners) additional corners can be installed and commissioned on a corner by corner basis. There may be a mesh disconnector between the transformer tee-off and the mesh corner. The items controlled by the mesh corner unit are the mesh circuit breakers, line disconnectors (if motorised) and the transformer disconnectors. The LV circuit breakers are controlled by an independent unit with which the mesh corner unit is intended to interface. Plant type L circuits These are typically overhead lines for DAR REQUIRED functions and cable circuits for DAR NOT REQUIRED functions. Inputs from the plant voltage transformer monitoring relays are used as a voltage reference. Delayed automatic reclosure facilities are provided for two circuits of plant type L, referred to as line A and line B. Plant type H circuits These are typically transformer feeders for DAR REQUIRED functions and transformers or reactors for DAR NOT REQUIRED functions. Inputs from the plant voltage transformer monitoring relays are not required as a voltage reference. Delayed automatic reclosure facilities are provided for two circuits of plant type H, referred to as trans A and trans B. Description - Scheme Scheme initiating enabling conditions Automatic isolation is initiated by protection operation. Delayed automatic reclosure is initiated by protection operation and a line voltage reference up to the point of trip. Automatic reclosure for a specific breaker is enabled provided that: – the circuit breaker is closed prior to the protection operation – the operation of the breaker is not inhibited – automatic reclosure for that circuit breaker is not switched out of service and is not locked out. Figure 2: Maximum configuration. Scheme Operation Plant type L circuits DAR REQUIRED If the incident line remains dead, mesh breaker CBX will reclose to charge the line. If the line becomes live during the dead time of the reclosing breaker, the breaker will revert immediately to closure with synchronism check. If the circuit trips within the reclaim time, following the dead bar/dead line closure, no further reclosure on to the faulty circuit will be attempted, instead the faulted circuit will be isolated by opening disconnector LDA for line A or LDB for line B, provided that DAR is selected in service. The mesh will then be restored by closing CBX, CBY and then CBZ. If DAR is selected out of service, the mesh circuit breakers will be locked out to prevent reclosure by associated units. DAR NOT REQUIRED If the incident circuit trips on fault, no reclosure on to the faulted circuit will be attempted. The faulted circuit will be isolated by opening the disconnector LDA for line A or LDB for line B. Provided that DAR is selected in service, the mesh will be restored, otherwise DAR on the mesh breakers will be locked out. INTERTRIP The receipt of an intertrip signal from a remote station will initiate and then inhibit the delayed automatic reclose of mesh circuit breakers for the period of time during which the intertrip signal is received. If the intertrip signal is maintained for a period of time in excess of the intertrip receive timer settings, the associated line will be isolated by opening LDA for line A or LDB for line B and then the mesh restored. 3 Figure 3: Relay block diagram. Plant type H circuits INTERTRIP DAR REQUIRED The receipt of an intertrip signal from a remote station will initiate and then inhibit the delayed automatic reclose of mesh circuit breakers for the period of time during which the intertrip signal is received. If the intertrip signal is maintained for a period of time in excess of the intertrip receive timer settings, the associated line will be isolated by opening HDA for Trans A or HDB for Trans B and then the mesh will be restored. Following a fault on the feeder section, if the mesh corner remains dead and provided that DAR is selected in service, mesh breaker CBX will reclose to charge the transformer feeder. If the mesh corner becomes live during the dead time of the reclosing breaker, the breaker will revert immediately to closure with synchronism check. If the transformer circuit trips within the reclaim time following re-energisation, no further reclosure on to the faulty circuit will be attempted; instead the faulted transformer circuit will be isolated by opening disconnector HDA for Trans A or HDB for Trans B provided that DAR is selected in service. The mesh will then be restored by closing CBX, CBY and then CBZ. If DAR is selected out of service, the mesh circuit breakers will be locked out to prevent reclosure by associated units. DAR NOT REQUIRED The faulted transformer is immediately isolated by opening the disconnector HDA for Trans A or HDB for Trans B. Any reclosure sequence for the transformer LV circuit breaker is locked out and any reclosure sequence on the associated banked line of the transformer plant is inhibited until isolation of the faulted transformer is complete. Provided that DAR is selected in service, the mesh will be restored. Otherwise, DAR on the mesh breakers will be locked out. 4 Mesh Corners FERRORESONANCE Facilities are provided to either prevent the re-energisation of circuits while in a ferroresonant condition, by locking out the mesh and LV circuit breakers, or to suppress ferroresonance, by opening the appropriate disconnectors. Any two disconnectors may be assigned ferroresonance suppression facilities. DAR REQUIRED Delayed automatic reclosure facilities are provided for the re-energising of a faulted mesh corner. Automatic isolation of any associated plant type H circuits is immediately initiated. If DAR is selected out of service any plant type H will be isolated, and then DAR on the mesh circuit breakers locked out. DAR NOT REQUIRED The faulted mesh corner is immediately isolated by opening the plant type L and plant type H disconnectors and then locking out DAR on the mesh and LV circuit breakers. COMMON RECLOSE LOCKOUT A signal to cancel reclosure of mesh and associated LV circuit breakers is given. This signal is relayed to adjacent mesh corner units. SWITCHING IN/OUT OF SERVICE AUTOMATIC ISOLATION and DELAYED AUTOMATIC RECLOSE can be switched in or out of service from a remote point. DELAYED AUTOMATIC RECLOSE may only be switched into service while AUTOMATIC ISOLATION is in service. When AUTOMATIC ISOLATION is out of service, the OUT OF SERVICE amber indicator lights on the front of the MCU. Indications and Alarms The MCU has four light emitting diodes (leds) on the front panel for indications and alarms. The top two (red and amber) are in four groups: – status alarms 1 indicated by the red led being stably lit. This group includes lockout conditions and a ferroresonance alarm. – compound alarms indicated by the red led flashing. This group includes the plant DBI alarms. – status alarms 2 indicated by the amber led being stably lit. This group includes the plant and MCU inhibited alarms. – change alarms indicated by the amber led flashing. This group includes the switchgear failure alarms. The alarms are enabled when the appropriate condition occurs in the ladder logic, and can then be read without removing the MCU front cover, by a combination of keystrokes on the ACCEPT/READ and SELECT/RESET keys on the relay front panel. The third led (amber) is the out of service indication. The fourth led (green) is the relay healthy indication. Test facilities The LFAA relay provides the customer with the facility to test the following parameters: – to read the state (i.e. on or off) of each input to, and output from, the relay. – with the front cover removed, and the relay out of service, the state of each relay can be changed. Description-Hardware The MCU is housed in a 4U (178mm) high case suitable for either rack or panel mounting. The MCU uses plugin modules which are individually tested and calibrated in the factory. If necessary, modules can be exchanged without any need to recalibrate the relay. A power supply module converts power from a dc supply to internal voltage rails. A power failure monitoring circuit with alarm output contact is provided. contains non-volatile read/write memory (EEPROM) for settings and relay status information, read/write memory (RAM) for temporary data, and read-only memory (ROM) for the system and application software. The system software resides in one pair of ROM devices, and the application software in another, separate pair. By appropriate programming of the application ROM, either standard or special auto-reclose requirements can be satisfied. and testing output relays, are only available when the cover is removed and can be blocked under certain specific conditions. See the Service Manual and Scheme Description for details of the conditions under which the commands are blocked. Five pushbuttons, arranged in a cruciform pattern, become accessible when the front cover is removed; four of these act as cursor keys for selecting commands or altering parameters in an easy to follow menu approach. The power supply module converts the auxiliary dc voltage into the regulated dc voltage rails required by the relay. High efficiency and isolation from the auxiliary supply are achieved by the use of a switching dc/dc converter. A power fail monitoring circuit with two alarm output contacts is included. The SET key at the centre is used to confirm entry of new settings. A parallel socket can be used to send information about the relay to a parallel printer. In addition, test points within the relay can be monitored on the parallel socket. Remote communications User Interface The front panel operator interface, shown in Figure 4, consists of a 2 row 16 character alphanumeric liquid crystal display (lcd) together with a seven push-button keypad. With the relay cover in position only the SELECT/RESET and ACCEPT/READ keys are accessible. Using just these two keys, it is possible to view system details, view (and clear) alarms, view counters, view settings, view the status of all opto-inputs and output relays and perform a timer test. A menu approach has been adopted such that the operator, using the lcd, can easily and efficiently access a whole range of useful information. All menu options may be configured on a PC and then transferred into the Mesh Corner Unit via its RS232C serial communications port. Sockets are provided on the front of the relay for temporary connection and on the rear for permanent connection. The rear socket can also interface with a modem for communication over a suitable link, for instance a telephone line. Security related commands, such as changing settings, resetting counters Three status input modules receive external plant status and protection equipment status signals via optoisolated inputs. Three output relay modules are provided. A 16 bit microprocessor is used for sequence control and timing functions. It interfaces with the opto-isolated inputs and output relays via an address/data bus. A block diagram is shown in Figure 3. Input and output connections are shown in Figures 5 and 6 respectively. The microprocessor module also Figure 4: Operator interface. 5 Figure 5: External connections to opto-isolator inputs. 6 Figure 6: External outputs contacts wiring. 7 Description-Software The relay software is divided into three main groups: the system software, the logic controller software, and the scheme logic. The system software is independent of the application and is common to all multi-modular hardware applications. It consists of various diagnostic, debugging, input/output, and multitasking handling facilities. It provides a common software environment, within which different application programmes can be developed and operated. The scheme logic is the application programme, defining how a relay performs; it is presented in the form of a ladder diagram. The ladder is an easy to follow application diagram, consisting of contacts, timers, counters and output relays. This approach means that the user does not need to understand complex programming languages in order to understand the relay application. Each relay scheme is fully documented including a copy of the ladder diagram appropriate to that scheme. The logic controller operating system interfaces between the system software and the scheme logic of the application programme. It processes the status input information, updates the relay outputs and controls the operator interface. Technical Data Auxiliary voltage rating Auxiliary voltage Vx (1) (dc) (Relay power supply) Nominal (V) 24/27 30/34 48/54 110/125 220/250 Operative range (V) 19.0 - 32.0 24.0 - 40.0 37.5 - 65.0 87.5 - 150.0 175.0 - 300.0 Auxiliary voltage Vx (2) (dc) (Opto-isolator supply) Nominal (V) 24/27 30/34 48/54 110/125 220/250 Operative range (V) 19.0 - 32.0 24.0 - 40.0 37.5 - 65.0 87.5 - 150.0 175.0 - 300.0 Note: Vx (2) may be different from Vx (1) Burdens (maximum) Vx (1) or Vx (2) (Volts) 24 27 30 34 48 54 110 125 220 250 8 Aux supply (W) (No output relays on) 8 8 8 8 8.5 8.5 8.5 9 10.5 11.5 Add to auxiliary supply burden (W) Each input 0.025 0.030 0.030 0.040 0.060 0.090 0.110 0.150 0.250 0.350 Each output RL0-RL7 RL8-RL13 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 Timers Timer name Limits of settings (s) Accuracy greater of: CBX dead bar time CBX dead line time CBX reclaim time CBX DBI time CBY dead bar time CBY dead line time CBY reclaim time CBY DBI time CBZ dead bar time CBZ dead line time CBZ reclaim time CBZ DBI time CB close pulse LDA opening time LDA DBI time LDB opening time LDB DBI time HDA opening time HDA DBI time HDB opening time HDB DBI time Intertrip LDA Intertrip LDB Intertrip HDA Intertrip HDB CB operation timer LDA operation timer LDB operation timer HDA operation timer HDB operation timer Ferroresonance 1.00 - 127 1.00 - 127 1.00 - 127 1.00 - 127 1.00 - 127 1.00 - 127 1.00 - 127 1.00 - 127 1.00 - 127 1.00 - 127 1.00 - 127 1.00 - 127 1.00 - 127 1.00 - 127 1.00 - 127 1.00 - 127 1.00 - 127 1.00 - 127 1.00 - 127 1.00 - 127 1.00 - 127 1.00 - 127 1.00 - 127 1.00 - 127 1.00 - 127 1.00 - 127 1.00 - 127 1.00 - 127 1.00 - 127 1.00 - 127 1.00 - 127 ±2% ±2% ±2% ±2% ±2% ±2% ±2% ±2% ±2% ±2% ±2% ±2% ±2% ±2% ±2% ±2% ±2% ±2% ±2% ±2% ±2% ±2% ±2% ±2% ±2% ±2% ±2% ±2% ±2% ±2% ±2% or or or or or or or or or or or or or or or or or or or or or or or or or or or or or or or –10 –10 –10 –10 –10 –10 –10 –10 –10 –10 –10 –10 –10 –10 –10 –10 –10 –10 –10 –10 –10 –10 –10 –10 –10 –10 –10 –10 –10 –10 –10 +20ms +20ms +20ms +20ms +20ms +20ms +20ms +20ms +20ms +20ms +20ms +20ms +20ms +20ms +20ms +20ms +20ms +20ms +20ms +20ms +20ms +20ms +20ms +20ms +20ms +20ms +20ms +20ms +20ms +20ms +20ms Contacts Make and carry for 0.2s Carry continuously Break 7500VA (30A or 300V ac or dc maxima) 5A ac or dc ac 1250VA dc 50W resistive 25W inductive, L/R=40ms (subject to maxima of 5A or 300V) Durability Loaded contact Unloaded contact 10,000 operations minimum 100,000 operations minimum 9 High voltage withstand Dielectric withstand IEC 255-5:1977 2kV rms for 1 minute between all case terminals connected together and the case earth terminal. 2kV rms for 1 minute between all terminals of independent circuits, with terminals on each independent circuit connected together. 1kV rms for 1 minute across open outgoing contact pairs. High voltage impulse IEC 255-5:1977 Three positive and three negative impulses of 5kV peak, 1.2/50µs, 0.5J between all terminals of the same circuit (except output contacts), independent circuits, and all terminals connected together and case earth. Electrical environment High frequency disturbance IEC 255-22-1:1988 Class III 2.5kV peak between independent circuits and between independent circuits and case earth. 1.0kV peak across terminals of the same circuit (except metallic contacts). Fast transient disturbance IEC 255-22-4:1992 Class IV IEC 801-4:1988 Level 4 EMC Compliance 89/336/EEC EN50081-2:1994 EN50082-2:1995 Product Safety 72/23/EEC EN61010-1:1993/A2:1995 EN60950:1992/A3:1995 4kV, 2.5Hz applied directly to auxiliary supply. 4kV, 2.5kHz applied directly to all inputs. Compliance with the European Commission Directive on EMC is claimed via the Technical Construction File route. Generic Standards were used to establish conformity. Compliance with the European Commission Low Voltage Directive. Compliance is demonstrated by reference to generic safety standards. Atmospheric environment Temperature IEC 255-6:1988 Storage and transit -25°C to +70°C Operating -25°C to +55°C IEC 68-2-1:1990 Cold IEC 68-2-2:1974 Dry heat Humidity IEC 68-2-3:1969 56 days at 93% RH and 40°C Enclosure protection IEC 529:1989 IP50 (dust protected) Mechanical environment Vibration IEC 255-21-1:1988 10 Response Class 1 Figure 7: Case outlines. Cases Further Information Type LFAA relays are housed in multi-module MIDOS cases. (See Figure 7). Application notes: Publication R4099 Service manual: Publication R5936 Information required with order DARCOM user guide: Publication R5940 Type of relay LFAA 103 Quantity required Auxiliary supply voltages Vx(1) and Vx(2) Case mounting Rack or panel 11