Several key technologies for substation automation transformation

1 Main contents of substation transformation The conventional substation is transformed into an unattended substation. First, the primary and secondary equipment must be modified to meet the unattended operation requirements.
1.1 Primary equipment major transformation and technical requirements
1.1.1 Renovation of the circuit breaker: The main requirement is to realize the remote operation function and provide a reliable circuit breaker position signal. For the operation requirements of 6~35kV oil circuit breakers that have been used for a long time and whose performance cannot meet the requirements of power grid operation, they should be replaced by oil-free equipment with good performance, high reliability and small maintenance (such as vacuum circuit breaker or SF6 circuit breaker). The auxiliary contact of the circuit breaker is modified to double auxiliary contact wiring to prevent signal misfire.
1.1.2 Renovation of high-voltage switchgear: improve the mechanism of preventing misoperation of machinery; improve the distance between cabinets, require insulation to support the insulation, have good flame retardant performance; strengthen the insulation level between bus conductors and relative ground; The current transformer in the switchgear cabinet meets the requirements of the insulation level, peak and short-time withstand current, and short duration of the high-voltage switchgear.
1.1.3 Reconstruction of over-voltage protection equipment: such as automatic tracking and automatic tuning of arc-extinguishing coils for neutral points of 6~35kV in substation; to reduce the operation and maintenance workload of substation, reduce residual voltage and prevent lightning arrester The explosion, the 6 ~ 35kV arrester of the substation should be replaced with a gapless metal oxide surge arrester (MOA).
1.1.4 Reconstruction of auxiliary components related to main transformer: Renovation of neutral point isolation switch and its operating mechanism can realize remote control operation; local and remote remote adjustment operation for on-load tap changer; realization of main transformer temperature remote measurement, etc. .
1.2 The modification of the secondary equipment and the requirements of the control circuit should be able to adapt to the unattended needs. The main requirements are as follows: 1 After the circuit breaker control circuit is modified, it should be simple, reliable and flawless. 2 When the circuit breaker control circuit is disconnected and the control power is lost, remote alarm should be realized and the control circuit fault signal should be retained. 3 The protection circuit is separately provided with a substation of the fuse. After the DC of the protection circuit disappears, it can alarm remotely. 4 The reclosing device should realize automatic retraction. After the remote control and local operation are closed, the reclosing power supply should be automatically input, and the reclosing discharge circuit will be automatically disconnected. After the remote control and local operation trip, the reclosing power is automatically exited, and the reclosing device is automatically discharged. Acceleration after reclosing and one reclosing as needed. 5 When the low frequency load shedding device or other system stability measures device trips, the recloser should be automatically blocked. 6 Cancel the non-corresponding flash function of the circuit breaker position signal, and the signal lamp is changed to energy-saving lamps such as LEDs. 7 Add remote control and local jump and closing lock loop. 8 The relevant circuit of the central signal device is modified accordingly.
2 Selection of transformation plan For the unmanned transformation of conventional substation, the general guiding ideology is “safe, reliable, practical and economical”. The secondary equipment transformation task is heavy and the transformation is difficult. It is necessary to explore some key technologies and find appropriate solutions. Here are a few typical secondary equipment retrofit options.
2.1 Reconstruction plan for the combination of circuit breaker control and relay protection
All the protection equipment is retained during the transformation, and the control panel (centralized console, centralized control cabinet) is cancelled, and the circuit breaker control loop and control equipment are installed to the appropriate standby position of the protection screen. This solution will cancel all the light board signals, measuring instruments and audio signals on the control panel. In order to meet the local operation and the monitoring requirements of the operation status of the equipment operated by the substation during the transition period, an RTU local workstation and display equipment shall be added. Display a wiring diagram, measurement information, accidents and notices on the display. With this modification scheme, the secondary circuit wiring can be simplified, a large number of control cables can be reduced, contacts in the loop can be reduced, and the operational reliability of the secondary equipment can be improved. This transformation scheme is suitable for the control loop transformation of multiple equipment combinations such as weak current control, centralized control console, and centralized control cabinet.
Substation transformation generally uses a conventional RTU device. The substation without RTU device can adopt the distributed distributed RTU telemetry AC sampling with better performance, and the communication connection between each RTU. In the existing RTU device of the substation, the function is expanded in the original device, and the RTU capacity is increased to meet the requirement of unmanned conversion information.
2.2 Only retrofit secondary circuit wiring scheme This modification scheme protects equipment and control equipment. In the transformation, according to the technical requirements of the unattended substation, part of the wiring in the secondary circuit, such as the circuit breaker control wiring reconnection, reclosing the wiring reconnection, and signal reconnection, etc.; add and replace some relays, so that It has the technical requirements of an unattended substation. This kind of scheme has the least amount of modification and small variation of the secondary circuit. It is the most convenient and economical transformation scheme to protect the substation by electromagnetic relay. The RTU unit of the substation uses conventional telecontrol equipment.
2.3 Renovation plan for all new secondary protection equipment For substation with long operation period, all the substation and protection equipment can be updated according to the technical requirements of unattended transformation during the design of the scheme. Integrated automation device. This kind of transformation scheme has a large investment, and generally only applies to the relatively old substation, and the original secondary circuit has not reached the safety requirement.
3 How to remotely monitor
3.1 The update of the relay is based on the actual situation of the unmanned transformation of the traditional substation, and also to ensure the realization of the “four remote” function, the current, voltage, time, signal, reclosing and other electromagnetics in the protection and automatic device The relays are all updated to static relays. Compared with the original electromagnetic relay, the static relay composed of the integrated circuit has the advantages of setting and intuition, low power consumption, quick action, high precision, etc., and the current and voltage relays add DC auxiliary power, and the normal operation of the relay can be performed by the power monitoring lamp. Monitoring, which greatly improves the reliability and quickness of protection. In particular, the signal relay has both electrical retention and magnetic retention, reliable signal memory, and multiple sets of moving contacts and electric regenerative loops. The realization of the "remote message" function and the remote reset of the signal relay are guaranteed.
3.2 Remote control and local operation conversion substation to achieve unattended operation, to facilitate equipment maintenance and emergency treatment at the accident site, it is necessary to realize remote control and local control operation, so the original KK control must be removed. Switch, add QK switch with “remote control” and “local” conversion function in the loop. Under normal conditions, all the operating or standby state circuit breakers of unattended substation must be placed in “remote control”. Location, remote control by the monitoring center attendant.
4 line monitoring
As we all know, in addition to reflecting the actual position of the circuit breaker, the red and green signals are also responsible for monitoring whether the trip circuit is normal. Although the traffic light can be monitored by traffic lights in the substation, it cannot be remotely For monitoring, the trip position relay TWJ and the closing position relay HWJ are added to the control circuit. As long as the two normally closed contacts of HWJ and TWJ are closed at the same time, it indicates that there is a problem in the trip circuit and it is necessary to go to the site for maintenance.
5 remote letter implementation
Conventional substationes need to be unattended, and the principle must have the remote signaling function through the various signals of the central signal and the photon card reaction. At the same time, after the relay is activated, it must be able to remotely reset at the monitoring center. Therefore, the problem of remote signaling of signal relays and the return of signal relays has become a key issue that should be taken seriously in the transformation.
5.1 Realization of remote signal After the original central signal of the substation is released, in order to correctly reflect all abnormal and accident signals in the station, the above signal must be provided to the remote moving device through the relay contact to realize the remote signal function. In accordance with the requirements of unattended operation, at the same time as reflecting the specific protection action events, the action and abnormality of any protection device of the substation shall start the total signal of the remote communication accident of the substation to remind the monitoring personnel to deal with it in time. In response to this requirement, the signal relays were all replaced with static integrated relays with electric return coils and multiple sets of moving contacts. Each signal relay provides a separate pair of empty contacts to reflect specific protection action events, and each relay provides a pair of empty contacts and connects these empty contacts in parallel to reflect the total fault signal. The actual operating position of the circuit breaker is reflected by the auxiliary contacts of the switch.
5.2 Signal relay's reset signal relay is replaced with a static relay, which has an electric return coil inside. In this way, the reset button on the signal relay can be reset locally, and the voltage of all the signal relays can be reset in parallel and connected with the normally open contact of the on-screen signal reset relay of the monitor screen remote control to realize the signal of the whole station. Remote control always returns. The problem of signal resetting for unattended substations is solved.
6 Summary Through practice, the substation realizes unattended operation, and its superiority can be roughly summarized as follows: 1 transmission load and power limiting speed are fast, voltage adjustment is rapid, thereby improving grid voltage quality, stabilizing grid operation, and improving reactive power management level; 2 Prevent accidents and speed up accident handling: Due to the notice signal, accident signal, and various over-limit signals to provide dispatcher analysis, measures can be taken to prevent accidents. After the accident is turned off, the dispatcher directly judges and performs remote control operation to speed up accident handling. It can avoid the accident expansion and shorten the accident handling time; 3 save a lot of personnel and improve the labor productivity of the enterprise; 4 remote control is directly executed by the dispatcher, without intermediate links, and it is not easy to misuse.

XUNDA Electric Oven three-dimensional temperature control,make the food more delicious and more even
10 section circulation baking,
baking become so simple from now on


REMOVABLE GLASS DOOR
Triple glazing glass doors can be removed and re-attached sasilyfor cleaning.The doorframe can also be completely removed from

oven for cleaning needs.


GRADE A RATING

Three layers of glazed glass increases the safety of the oven greatly.Reflective inner glass ensures the outer door to always be safe to touch.This design. feature allows peace of-mind when operating oven.


Electric Oven

Electric Ovens,Electric Convection Oven,Electric Toaster Oven,Built In Gas Electric Oven

Xunda Science & Technology Group Co.ltd , http://www.xundatec.com