The period of operation or service life of a device before write-off is determined by the moral or physical wear and tear of the device to such a state that its restoration becomes unprofitable. The service life of the device, starting with the test when it is turned on again, usually includes several periods between repairs, each of which can be divided into stages characteristic from the point of view of reliability: the running-in period, the period of normal operation and the wear period.
The following are installed types of scheduled maintenance URZA :
· check when switching on again (adjustment) ( N);
· first preventive control ( K1);
· preventive control ( TO);
· preventive restoration (repair) ( IN);
test control ( T);
· testing;
· technical inspection.
In addition, during operation the following types of unscheduled maintenance can be carried out: extraordinary and post-accident inspections.
Checks when switching on again URZA, including secondary circuits, instrument transformers and drive elements of switching devices related to URZA, are carried out before switching on newly installed devices and after reconstruction of existing devices associated with the installation of new additional equipment, alteration of equipment in operation, or after installation of new secondary chains.
Maintenance task during the running-in period taking into account the features of relay protection is to identify run-in failures and prevent operational failures for this reason. For URZA, running-in failures are most typical in initial period operation. During other periods between repairs they occur much less frequently.
The running-in period begins with adjustment work before putting the device into operation, which, if carried out carefully, ensures the identification and elimination of most of the running-in failures. However, there is always a possibility that some defects will not be detected or will appear after adjustment. In addition, during setup, hidden defects in elements may not appear, which will become apparent some time after the device is put into operation. These may include, for example, weakened turn-to-turn insulation of relay and transformer windings, the presence of breaks in resistance wires, hidden defects in electronic equipment.
Thus, with the completion of adjustment work and commissioning of the device, the running-in period cannot be considered complete. It is necessary to carry out another check some time after commissioning, after which it can be considered with a fairly high probability that run-in failures have been identified and eliminated. This check is called first preventive control . The timing of this control is determined mainly by two contradictory factors. On the one hand, it takes some time for hidden defects to appear and, therefore, the longer this time, the more likely their manifestation. On the other hand, with an increase in the interval between putting the device into operation and the first preventive control, the likelihood of device failure increases.
The task of maintenance during the period of degradation is timely preventive restoration or replacement of worn-out device elements in order to prevent a sharp increase in the failure rate parameter. The corresponding type of maintenance, taking into account the maintainability of most URZA elements, is named preventive restoration .
The frequency of preventive restoration of a device is determined by the frequency of restoration of its elements, which in turn is determined by the resource of these elements.
Maintenance task during normal operation, i.e. between two restorations, is to identify and eliminate any failures that have occurred and changes in device parameters in order to prevent possible operational failures. The corresponding types of maintenance are called preventive control and test control. Prophylactic control consists of checking the performance of the entire URZA. Test control, as an additional type of maintenance, it is used for microelectronic and MP devices that have the appropriate built-in tools. During test control, the functionality of a part of the device is usually checked.
The frequency of preventive and test monitoring is determined by a number of factors: failure flow parameter; performance requirements flow parameter; damage from failure to operate the URZA; costs of preventive control; the likelihood of personnel errors in the process of preventive control.
In addition to preventive monitoring, during normal operation it is provided, if necessary, periodic testing . The purpose of periodic testing is to additionally check the performance of the least reliable elements of the relay protection devices: time relays with a clock mechanism, process sensors, drives of switching devices (actuators).
In case of partial changes in circuits or reconstruction of emergency protection devices, when restoring circuits broken due to the repair of other equipment, if necessary, changes in settings or characteristics of relays and devices are carried out extraordinary inspections . Post-accident checks are carried out to find out the causes of operational failures or unclear actions of the automatic control protection equipment.
External technical inspections of equipment and secondary circuits, checking the position of switching devices and test blocks should be carried out periodically.
In order to ensure correct and reliable operation of relay protection devices, it is necessary to periodically check them. The frequency of inspections is established taking into account the responsibility of the facility, the condition of the equipment, the qualifications of the operating personnel and other factors specific to each specific case.
The following types of checks exist.
Checking when switching on again, which is carried out during commissioning of a relay protection device or electrical automation device, as well as during their reconstruction and is carried out to the fullest extent.
A complete scheduled check, the scope of which, as a rule, is significantly less than the scope of the check when switching on again and is established for each device based on operating experience. The purpose of a full scheduled check is to ensure that the device is in good condition and that the settings of its basic parameters remain unchanged. A full scheduled inspection should be carried out, as a rule, once every 2-3 years. The first scheduled check is usually performed 1 year after the new switch on.
A partial scheduled check designed to additionally check elements or. devices that have reduced reliability or are in particularly difficult conditions (exposed to dust and contamination, exposure to high and low temperatures, dampness, chemical precipitation, etc.). Partial scheduled checks are carried out in the intervals between full ones, and their frequency and scope are determined by local relay protection services.
Additional check, which is performed if it is necessary to change settings, partially change the circuit, determine the causes of unnecessary operations or device failures, etc.
Testing of turning off and on switches or other equipment installed in primary circuit. Testing is carried out to check the serviceability of switching equipment, as well as relay protection circuits.
In addition to inspections, relay protection service personnel must periodically (once every few months) inspect relay protection devices, automation, control and alarm circuits. Inspections are carried out to check the compliance of the condition of equipment, linings, test blocks, etc. with the operating mode of electrical equipment.
Protection tests should be carried out whenever possible with the power equipment switched off. It is also possible to carry out security checks on switched-on equipment. If, in this case, the protection being tested is the only one or if the remaining protections in operation do not provide quick and reliable shutdown of short circuits, then temporary protections must be turned on for the duration of the test. As such, the protection of a bus coupling or bypass switch can be used, through which equipment with testable protection is switched on, or protection specially mounted for this purpose.
In some cases, when turning off the main high-speed protection to check, it is possible to improve the backup protection remaining in operation by changing its settings, for example, by reducing the operating current and time delay, even allowing in some cases the possibility of its non-selective action.
Testing relay protection devices consists of the following main steps:
– taking the protection out of operation and taking the necessary measures to ensure its safety;
– preliminary check of the unchanged settings and general state of the protection;
– external and internal inspections of the relay and checking the mechanical part of all equipment;
– checking the correct installation and marking of circuits;
– testing and checking of insulation;
– checking the correct choice of fuses and circuit breakers for operating current circuits;
– checking current and voltage measuring transformers, checking fuses and circuit breakers installed in secondary voltage circuits;
– checking the settings and electrical characteristics equipment;
– checking the interaction of all elements of the device circuit and the effect on switches and other switching equipment;
– checking equipment and control circuits;
– checking the device in a complete circuit with primary current from an external source, load current or current short circuit;
– putting the protection into operation and preparing the necessary documentation.
Relay protection and automation devices are operated by the local relay protection, automation and electrical measurement services of the MSRPZAI, therefore the OVB personnel inspects the RZAI devices, checks their serviceability and readiness for action at least once a month in the presence of telesignaling about device malfunctions and automatic monitoring of high-frequency channels (if absence, inspections are carried out at least once a week). When visiting a substation for other reasons, the OVB personnel conducts checks of the RZAI devices to the same extent.
When inspecting relay protection, automation and measurement devices, they become familiar with the entries in the relay protection log about all work performed during the period of absence of OVB electricians at the substation, changes in settings, circuits, relay protection devices introduced again or taken out of service, with entries in the operational log . Check the serviceability of emergency and warning alarms, as well as switch position alarms, the presence of voltage on the operating current buses, all sources of direct and alternating current and operating mode under chargers. Monitor the insulation resistance of operational current circuits using stationary devices. Using the alarm system, they check the serviceability of control purposes for switches and other switching devices, the presence of operative current in all devices and circuits of relay protection, automation, alarms, control, the serviceability of fuses and ATS of operative current sources, the correct position of circuit breakers, switches and other switching devices in the ATS circuit and compliance of their provisions with the primary scheme. Using installed measuring instruments and alarms, the serviceability of voltage transformer circuits, fuses, and the correct position of all switching devices in these circuits are monitored in accordance with the actual primary connection diagram.
Inspect all protection and automation devices on the control panel, relay panel, in the corridors of the switchgear, switchgear, checking their serviceability and readiness for action according to appearance or, if possible, by alarm. Indicator relays that were triggered by accidental causes (for example, shocks) are returned to their initial position (state). Check the correct position of all control elements of the relay protection devices and the compliance of their positions with the actual primary circuit of the substation. Inspect and check the serviceability and readiness for operation of fixing instruments, recording measuring instruments and oscilloscopes (they also check the supply of paper and ink for recording instruments, paper or film for oscilloscopes). Inspect gas relays of transformers (for relays with an inspection window, check the housing for the absence of air). Check the position of the drives of switches, disconnectors, separators and short circuiters, seals of doors and covers of relay cabinets, etc.
All faults identified during the inspection are recorded in the relay protection log and immediately reported to the dispatcher of the power plant (RES) and the MSRPZAI personnel.
OVB personnel can eliminate some malfunctions or deviations from the specified mode in relay protection devices. These include:
turning on circuit breakers or replacing fuse links in the circuits of voltage transformers or power supply of relay protection and automation devices (if the switches are repeatedly disconnected or the fuse links burn out, the OVB electrician, senior in the shift, informs the dispatcher and acts on his instructions);
decommissioning of all relay protection devices in the event of a break in the shutdown circuit of a switch or other switching device (the break is detected by an alarm) with subsequent implementation by the dispatcher of the measures provided for the connection that has completely lost relay protection;
decommissioning of all relay protection devices operating from damaged individual power supplies, capacitor chargers and capacitors in the trip circuit of the circuit breaker, separator, short-circuiter, followed by the dispatcher carrying out the measures provided for this connection, which has lost all protections;
determination of the location of damage when a ground fault appears in the operational current circuits (with the permission of the dispatcher, using local instructions);
disabling devices that act on the automatic closing of the circuit breaker in case of damage to the rectifiers supplying the switching circuits of electromagnetic drives (damage is detected by a decrease in the rectified voltage, measured by a voltmeter, and by external inspection of the rectifiers). When the RZAI devices are triggered, various light and sound alarms operate on the control panel, as well as a remote alarm. By dropping the flags of the indicating relays, the EOD personnel determine which device and which zone of it have been triggered (according to the inscriptions on the relay), and then carry out the alarm operations prescribed by local instructions (disabling sound signal, switching on the switch position indicator, etc.). By external inspection and alarm, the OVB personnel identifies the nature of the damage that caused the operation of the relay protection devices, makes an entry in the relay protection log and at the same time informs the dispatcher.
In switching devices that have changed their normal position, the control keys are acknowledged in cases where the automatic reclosure and automatic transfer devices did not work successfully. EOD personnel inspect all protection and automation devices and apply marks (for example, with chalk) on the covers of triggered indicating relays or next to them on panels.
At the same time, inspects automatic reclosure and automatic relay counters, recording their readings, as well as recording and recording instruments and oscilloscopes. The results of the inspection, recorded in the relay protection log, are reported to the dispatcher by the OVB personnel and, with his permission, return the indicating relays to their initial state, leaving time stamps until the end of the analysis of the operation of the relay protection devices and receipt of the dispatcher's permission.
After all operations are completed, the position of the indicator relay flags is re-checked (they must be raised), the position of all control elements of the relay protection and protection devices corresponds to the actual primary connection diagram, and the alarm system at the substation is returned to normal. The RZAI service is informed about the operations performed. Upon completion of the analysis of the operation of the relay protection devices, the time stamps on the covers of the indicating relays or panels are erased.
All work on RZAI devices put into operation is, as a rule, performed by MSRZAI personnel based on pre-filled requests. Having received permission from the dispatcher, the EOD personnel prepares the work site: performs the necessary switching on and off of primary equipment, operations with relay protection devices and the requirements of safety regulations; installs fences (curtains) blocking access to neighboring RZAI devices. Having checked the availability of RZAI personnel for the relevant work, he allows them to begin.
OVB personnel, at the request of operating personnel, perform the necessary switching on and off of completely disabled (with disconnectors disconnected) primary switching devices (switches, separators, short circuiters) for various tests and checks of the interaction of relay protection devices with primary equipment. In addition, he receives permission from the dispatcher for the personnel of the RZAI services to perform various switches on and off of energized equipment.
After completion of the work, the OVB personnel familiarize themselves with the entries made by the MSRZAI personnel in the relay protection log, with changes in the equipment on the device panels, carry out the measurements or testing provided for in the instructions, sign in the relay protection log and inform the dispatcher about the completion of the work and the readiness of the relay protection devices for commissioning action.
Operational control of all elements of relay protection, automation and alarm systems is carried out by OVB personnel only with stationary disconnecting devices (control keys, switches, overlays). When taking measurements, he uses only stationary, constantly switched on measuring instruments, self-resetting buttons or other switching devices for short-term measurements (in some cases, local instructions allow the use of portable current clamps, voltmeters, etc.). Action various devices OVB personnel tests using certain devices, but does not have the right to disconnect and connect wires and cables or use temporary jumpers.
1.1. The rules determine the types, frequency, programs and volumes Maintenance all relay protection and automation devices, current and voltage transformers, power supplies and other components of relay protection and automation devices used in electrical networks 0.4-35 kV.
1.3. The rules provide for an increase in the duration of the maintenance cycle and a reduction in the volume of operational checks of relay protection and automation devices in 0.4-35 kV networks.
1.4. The methodology for checking and testing specific relay protection devices is given in the relevant instructions and guidelines that should be used when carrying out maintenance.
2.1.1. Reliability is the property of a device to maintain over time, within established limits, the values of parameters that characterize the ability to perform required functions in given modes and conditions of use, maintenance, repairs, storage and transportation.
2.1.2. An operational state is a state of devices in which the values of parameters characterizing the ability to perform specified functions comply with the requirements of regulatory, technical and design documentation.
Gradual failures occur as a result of changes in one or more parameters of the device or the state of its elements due to various physical and chemical processes that arise as a result of prolonged operation.
In relay protection and automation devices, these processes include: dusting of internal parts of relays and devices, formation of carbon deposits and cavities on contacts, misadjustment of the mechanical part of the relay, loosening of screw contact connections, decreased insulation resistance, changes in the characteristics of the device or its individual elements. When timely preventive measures are carried out, these changes in the parameters or state of the device and its elements can be detected by monitoring and diagnostic methods, and possible failures can be prevented by adjusting, replacing or restoring the elements.
Sudden failures are characterized by abrupt changes in the values of one or more device parameters. The causes of sudden failures are physical and chemical processes that occur rather slowly over time.
Run-in failures occur during the initial period of operation and are caused mainly by shortcomings in production technology and insufficient quality control of component elements of devices during manufacturing. For relay protection and automation devices, the causes of running-in failures can also be errors during installation and commissioning, or poor quality of commissioning.
Failures during normal operation occur after the end of the running-in period, but before the onset of degradation failures. This is the longest period of total operating time in which the number of failures is approximately constant and has the least significance.
Degradative failures are caused by the natural processes of aging, wear and corrosion, subject to compliance with established rules, design, manufacturing and operation standards. These failures occur when the device as a whole or its individual elements approaches a limiting state due to aging or wear conditions at the end of its full service life or between repairs. With proper maintenance organization, these failures can be prevented by timely replacement or restoration of elements. In this case, the replacement period should be less than the average wear time of the element. If timely replacement is not carried out, the number of degradation failures increases.
2.1.4. Running-in failures, failures during normal operation and degradation failures are random events, but obey general laws.
2.1.5. It is necessary to distinguish between a failure of a protection device as an event of loss of functionality and a failure of operation as an event of failure to perform a specified function when a corresponding requirement arises.
2.2.1. The period of operation of a device or its service life before decommissioning is determined by the wear and tear of the device to such a state that its restoration becomes unprofitable.
The service life of the device, starting with the test when it is turned on again, usually includes several periods between repairs, each of which can be divided into stages characteristic from the point of view of reliability: the running-in period and the period of normal operation.
2.2.2. Checking (adjustment) of relay protection and automation devices when switching on again should be carried out when commissioning a newly installed, separate connection or when reconstructing relay protection and automation devices at an existing facility. This is necessary to assess the serviceability of equipment and secondary circuits, the correctness of connection diagrams, adjusting relays, and checking the functionality of relay protection and automation devices in general. The check when switching on again must be carried out by MS RZA personnel or a specialized commissioning organization.
If the check for new switching was carried out by a third-party commissioning organization, then switching on of new and reconstructed devices is carried out after their acceptance by the relay protection service.
2.2.3. Preventive monitoring of relay protection devices is carried out in order to identify and eliminate possible malfunctions of its elements that arise during operation, which can cause unnecessary operations or failures of operation of relay protection devices.
The first preventive control after putting the relay protection device into operation is carried out mainly in order to identify and eliminate run-in failures that occur during the initial period of operation.
Preparatory work. A complete set of design and factory documentation is selected, necessary instructions and test programs, approved settings for setting up protection devices and electrical automation (they are obtained from the relevant operating services). Using verified circuit diagrams, the wiring diagrams of panels and consoles, rows of clamps, cable logs, etc. are checked. When analyzing the circuit diagrams, the possibility of adjusting the specified settings on the design devices is checked, and relays that need to be replaced are identified.
A workplace is organized, the necessary testing devices, measuring instruments, tools and devices, passport protocols for all devices of the connection being established are prepared, and permission to work is issued.
To avoid erroneously applying voltage to adjacent panels and devices, all cables connected to the terminal rows of the panel being tested must be disconnected.
External and internal inspection. The compliance of the installed equipment with the design and specified settings is checked.
The correct marking of cables, cable cores, and wires is checked visually and by checking the continuity of the circuits; installation location and grounding of secondary circuits; the presence of the necessary inscriptions on panels and equipment, usually carried out by operating personnel.
On the device being adjusted (panel, switchboard, remote control), the compliance of the external installation with the circuit and wiring diagrams is checked, by rocking and tugging on the wire with tweezers, the reliability of the soldering is checked, all contact connections on the rows of clamps and devices are tightened. As a rule, the correct installation is not checked on standard serial panels.
During an internal inspection and check of the mechanical part of the equipment, the absence of visible damage, the reliability of bolted connections and soldering, and the condition of the contact surfaces are checked. By touching the relay with your hand, check the movement, movement and absence of rubbing of the moving parts, the presence of regulated backlashes, gaps, deflections, dips, etc.
A preliminary check of the insulation resistance is carried out to monitor the insulation resistance of individual units of the connection being established (control panels, panels, control cables, secondary windings of current and voltage transformers, etc.) before applying test voltage to them from testing devices. The measurement is carried out with a 1000--2500 V megohmmeter between separate groups of electrically unconnected circuits (current, voltage, operating current, alarm, etc.) relative to the ground and to each other. To ensure increased reliability, the insulation resistance is checked between the conductors of the gas protection cable and between the conductors of the cable from the voltage transformers to the cabinet where the protective elements are installed -- circuit breakers or fuses. Equipment not designed for a test voltage of 1000 V (for example, magnetoelectric and polarized relays) is excluded from the circuit during checks and is tested in accordance with factory standards.
Checking the electrical characteristics and adjusting the specified operating settings is carried out in accordance with the requirements of maintenance rules, current instructions, including factory ones, for this specific type of device.
The work of checking the electrical characteristics is completed by adjusting the specified settings, after which all secondary circuits of this connection are assembled by connecting cable cores on rows of terminals, with the exception of communication circuits with devices in operation.
Insulation measurement and testing is carried out in full assembled circuit with casings, covers, relays, doors, etc. installed and closed for each group of electrically unconnected secondary circuits. Electrical insulation strength is tested with a voltage of 1000 V AC for 1 minute relative to ground. Before and after applying an alternating test voltage, the insulation resistance of the tested circuits is measured with a megohmmeter of 1000-2500 V. Elements and circuits with an operating voltage of 60 V and below are excluded from these checks.
Checking the interaction of device elements. At an operating current voltage of 0.8, the correct interaction of the protection relay, electrical automation, control and alarm is checked. The interaction is checked in accordance with circuit diagram, by manually closing and opening the relay contact circuits, while checking the absence of bypass circuits, the correct operation of the circuit when switching overlays, switches, test blocks, etc. On the rows of terminals of the device being tested, the presence and absence of signals intended to influence devices located at work.
A comprehensive test is carried out according to an agreed and approved program by simulating various emergency modes at the rated voltage of the operating current supplied according to the design diagram from the switchboard direct current. For this purpose, various combinations of currents and voltages are supplied from the testing device to the connection under test, which correspond to the parameters of emergency modes (this test is carried out with the relay covers closed).
When simulating each mode, the operating time of each of the protection stages on the contacts of the output relays is measured, and the correct operation of interlocks and alarms is checked. To avoid repeated impacts on switches, disconnectors, valves, gate valves, etc., it is necessary to ensure reliable removal of output protection circuits from operation. After checks in various modes, all connections with other devices and devices are restored (especially carefully connect equipment that is in operation). A comprehensive test ends with testing the effect on switching equipment and monitoring interaction with devices of other connections.
The results of the check are recorded in the corresponding entry in the relay protection log, after which work in the operational circuits of this connection cannot be carried out without special permission.
Preparing the device for use. Before switching on, the panels and rows of clamps are re-inspected, the position of the connecting bridges and jumpers, the position of the overlays in the shutdown circuits, the absence of disconnected and bare wires and cable cores, and the presence of grounding in the corresponding circuits are checked.
When the equipment is turned on again, all protections, including those not tested by operating current, are put into operation with a shutdown effect; immediately after switching on, the devices are checked under load jointly by commissioning personnel and local service specialists, including operational personnel. This test of the device under load with operating current and voltage is final, confirming the correct activation and behavior of individual relays and the device as a whole. When checking the operating current and voltage, the correctness of the voltage circuits is first checked, and then by removing vector diagram currents and assessing it based on the actual direction of power in the primary network, the correct execution of current circuits is checked. To monitor the integrity of the neutral wire, the unbalance current in it is necessarily measured, and the creation of appropriate modes controls the flow of phase current through the neutral wire.
After completing the load test, carefully inspect and restore the jumpers on all relays whose mode changed when testing them with operating current. An appropriate entry is made in the relay protection log about the status of the tested devices and the possibility of putting them into operation.