Cubicle switchboard of cassette type – a perspective item of Open JSC «Energoprom»
Shmakov A.V., Director of the engineering centre of Open Society «Energoprom», Ozyorsk
In the nearest decades the high-voltage electrical engineering will still define the development of domestic electric power industry.
The major factors which determine the modern development of the high-voltage equipment in Russia, are the following: real demand for equipment; universal tendencies of this techniques development; active introduction of foreign companies onto the Russian market of the electrotechnical equipment; a significant share morally and physically out-of-date electrotechnical equipment under operation; impossibility to provide fast replacement of the worn out equipment owing to the general economics recession; research organizations potential decrease.
The demand for the high-voltage electrotechnical equipment in Russia owing to its physical deterioration and obsolescence is obvious. As the economic situation in the country does not allow completely simultaneously to replace the growing old equipment, there was set a task to electrical engineers of modernisation and reconstruction rates increase on the basis of modern types of the equipment introduction at simultaneous expansion of operational resource research works.
There is a huge backlog demand of low and average voltage electric equipment on the Russian market and this backlog demand in the nearest 2–3 years will grow only. The sub-station equipment market capacity is from 8000 up to 14000 items per year (from 48000 up to 84000 switch cells).
One should note, that new substation erection at the industrial enterprises is carried out basically on drawout cells type, but retrofit is carried out basically on the same type of cells what has been installed before (though there are also exceptions of this rule). Having addressed to foreign experience, we shall see, that the basic idea at new substations construction is the use of compact cells which enable to modernize substation without change of a building part. This is a very much important point since the basic charges, as a rule, are connected with capital construction, with additional cable linings in residential areas or on the industrial site. Modern substations with a high level of reliability allow to reduce the working costs on 85%.
«It is difficult to allocate unequivocal tendencies in the field of cubicle switchboard (CS) construction, but similar directions in new development are traced at many manufacturers. First of all one may mention the desire to reduce the mass and gross geometry of CS and KSO cells. Basically this problem is solved by sulphur hexafluoride or, to a lesser degree, firm insulation usage. Big enough number of the submitted cells means unilateral service and near-wall design, which considerably saves substations building space.
The next observation is connected with CS and KSO cells height reduction and with the relay protection and automatic equipment devices compartment moving onto convenient for the staff level. Especially obviously this tendency is observed in 0,4 kV cases, but similar exhibits have been submitted and in the average voltage class. If to speak about CS cells the priority of all leading manufacturers now is given to cassette type CSs with division of compartments and presence of a maximum quantity of the blockings for safe service. Linear CS compartments are designed basically for input of single-phase cables with polyethylene insulation that has allowed to reduce the cable compartment volume and to raise reliability in a number of designs. The majority of manu-facturers provide more reliable CS metal ware protection from corrosion (powder painting, zincing, and in some cases application of stainless steel), that considerably prolongs cells lifetime». (The Information from the Hanover industrial
exhibition held in April, 2005).
What is the state of the cassette design cells production now:
1. ABB produces ZS1 cells with own switch VD4 (in November, 2004 “ABB Silovyje Systemy” started this cells manufacturing in Russia, about 500 cells were supplied in 2005) and with the own «REF 542 Plus» microprocessor device.
2. «SCHNEIDER ELECTRIC» produces MCset and «Nexima» cells with own « Evolis» or LF1 switches and «SEPAM» microprocessor device.
3. «SIMENS» produces «NXair» cells with the switches of a 3AH1-5 series.
At the moment among domestic cassette-type cells manufacturers one may consider the following factories:
– «Vysokovol’tny Soyuz» with KU-6S, KU-10S (integration of RZVA and NTEAZ) cells with the switch of the Rovno factory which is produced under ABB license.
– Taurida Electric» with D-12P, D-12PT cells with the switch of own production;
– «SEShch» with K-68 cell, serial pro-duction is planned for 2006.
– «MEShch» with K-121 cell equipped with «Taurida» switch, start of production in 2006;
– «The Alliance-Electro» with K-26 AE cell, serial production is planned for 2006.
Taking into account recent tendencies, Open Society «Energoprom» have made a decision on development and production of home-made cassette-type cell of K-01ES series.
The CS cell is a metal ware, made of the high-quality zinced steel which details are made on the precision equipment. Connections are executed on strengthened steel exhaust rivets and carving connections. External elements of a design - front face doors, lateral panels of outside cells, etc. are powder painted (colour RAL 7032).
Reliability of cases and safety of the personnel are provided by:
– high durability of a case skeleton bearing construction made of steel sheets;
– presence of internal skeleton partitions for a case compartments with application of an epoxide leading-through cartridges;
– the stationary voltage indicator;
– presence of the mechanical and electro-magnetic operative blocking, which prevent wrong actions of the attendants;
– an opportunity of the visual control of a ground-wire knifes position in running cycles behind closed doors.
The case skeleton is divided by vertical and horizontal metal partitions into a relay compartment, a compartment of a sliding element, a compartment of modular trunks and a cable compartment in which there are also installed the current transformers, voltage and linear trunks. Channels above the compartments, supplied with special valves designed for heated air removal and exhausted gases emission at limiting short circuit currents switching as well as at open arch occurrence in compartments. For motionless current carrying contacts insulation as well as for modular trunks sectioning in the case, the epoxide leading-through cartridges are used. Due to this and to the arc protection, the failure is localized within one case compart-ment during necessary time.
The sliding element is located in the middle part of a case directly above a cable compartment and is structurally designed as the carriage which moves from working position into control position and back behind closed case doors. In repair position the sliding element by means of the inventory carriage from the complete set spare parts moves to a corridor of service, thus the shutter mechanism automatically blocks access to the case current-carrying contacts.
Depending on the circuit, the ground wire with a spring drive might be places in case; It is settled down on a cable compartment skeleton lateral wall and is actuated by means of the handle from the complete set spare parts.
The original design provides easy, convenient and safe access to the equipment. Current transformers along with the leading-through cartridge of the bottom motionless current-carrying contact are phase by phase mounted on separate metal partitions between compart-ment of sliding element and compartment of current transformers. These partitions have special covers for access to secondary circuits of current transformers. Due to such solution their service becomes simple as much as possible.
To access the contacts of secondary circuits of current transformers it is enough: to open a sliding element door and to roll out it on the inventory carriage into a corridor of service, then to dismantle a checked phase secondary circuits cover.
To replace the transformer of a current it is necessary to additionally dismantle an easily removable partition between a compartment of a sliding element and a cable compartment, to dismantle fixture on a carcass of a phase under repair, then the block of the transformer of a current together with the trunk and the leading-through cartridge of the bottom motionless contact turns on 90° into repair position.
To access the voltage transformers and cable cutting it is enough to open a cable compart-ment door (in which case the sliding element can be located in a case in control position, and ground wire be switched on).
The described cases design allows starting CS manufacture with real, instead of declared single-end service. K01-ES series cases have no doors and hatches for access to elements of a case from the back side.
According to service conditions – single-end service cases have a corridor of service at the front side of the cases, equal to1800 mm.
It is admitted the installation of CS cases with pass from the back side, in this case from the back side of a case the demountable covers for access to elements during repair work are anticipated.
All necessary protection under working standards and blocking In CS cases are anticipated:
– moving the switched-on switch from control position into working position;
– moving the switched-on switch from working position in control position;
– moving the switch into intermediate position (between working and control);
– moving a sliding element from control position into working at the switched-on ground wire knifes;
– the ground wires witching-on at working or control position of a sliding element.
Besides the following blocking are in additionally realized:
– impossibility of a cable compartment door opening when the switch is not moved to control position, the ground wire is switched off and then it is not switched-on;
– impossibility to roll the switch into working position when a cable compartment door is open.
Operative electric blocking is carried out according to circuits of auxiliary electric connections.
The excess-voltage suppressors are mounted in cases if necessary.
Documents and guarantees
In design approaches and solutions when CS of K01-ES series development the patent cleanliness of production is kept, design solutions are protected by copyrights according to the current legislation.
CS Cases are made in the conditions which are controlled by quality management system according to ISO 9001:2000 requirements.
Cases life-time before decommissioning is not less than 25 years under conditions of before-the-fact replacement of the completing equipment, which life time less than 25 years, and under carrying out the maintenance service according to the maintenance instruction. A warranty period of operation is 3 years from the date of commissioning.
It is necessary to note, that all measuring current and voltage transformers used in cases, are certificated, put into state register of measuring means, have the metrological certifi-cate and can be used for the current consumption commercial record.
All suggested equipment requires the minimal maintenance service at operation or does not require it at all during whole life time of 25 years.
The basic advantages of K01-ES cells
1. Wide scale of CS cases with various switches (both vacuum and sulphur hexafluoride).
2. The minimal maintenance service during operation.
3. Use of the modern programmed protection block made on the microprocessor of the various manufacturers, supplied with the information display.
4. A universal set of electric accessories.
5. Fast and simple replacement of electric accessories.
6. The increased staff safety at possible ground wire switching -on on to short circuit, possibility for ground wire to be switched onto the current of the case thermal stability, i.e. short circuit full current of modular trunks without damages.
7. An opportunity of a voltage transformer installation in a cable compartment, immovable or on the drawout element.
8. Application at the request of the customer of capacitor voltage indicators to control the availability or to measure the voltage in the main circuits.
9. The opportunity of insulated trunks use for cases on rated voltage of 10 kV and is higher.
10. An opportunity of single-end service.
11. Linear connection by Cable or buses.
12. Maintenance of the comprehensive blocking system which prevents the incorrect actions of the attendants.
13. Doors at all high and low voltage compartments.
14. An opportunity of drawout element moving from the working position into the control position and back and an opportunity of mechanical, emergency switching-off of the switch without door opening.
15. Support of the attendants full safety at insulation overlapping in internal compartments.
16. Seismic stability up to 9 points under the Richter scale.
17. Guaranteed retrofit when new generation switches development.