WO2007064265A1

WO2007064265A1 - Substation

Info

Publication number: WO2007064265A1
Application number: PCT/SE2005/001817
Authority: WO
Inventors: Bertil Nygren; Harvinder Ghatta; Stefan Rosenlund; Stig Holst; Sven-Anders Lejdeby
Original assignee: Abb Research Ltd
Priority date: 2005-11-30
Filing date: 2005-11-30
Publication date: 2007-06-07

Abstract

An outdoor substation for high voltage comprising at least one bay containing at least one line including a switchgear apparatus, a control system and power supply means.

Description

Substation

TECHNICAL FIELD

The present invention concerns a substation for controlling the transmission of electric power. More precisely the invention concerns an outdoor substation intended for switching high voltage (HV) power transmission. By high voltage in this context should be understood a voltage preferably above 72 kV.

BACKGROUND OF THE INVENTION

A high voltage substation comprises a plurality of switchgear apparatus and a control system for controlling the electric power transmission. The control system comprises a plurality of sensing means, such as current transformers and voltage sensing means, and computer means for controlling the switchgear apparatus and for communication with the sensing means. The substation also comprises electric power supply means for power supply of the switching apparatus and the control system. To provide an uninterrupted power supply the power supply means comprises energy storage devises. Such energy storage device preferably comprises battery means.

Typically an outdoor substation comprises a great number of switchgear apparatus. Commonly there are some 40 switchgear apparatus or more in a high voltage substation. The outdoor substation comprises at least one incoming line and may comprise a transformer connected to the incoming line. The substation also comprises a plurality of power lines for outgoing power organized in bays. Thus, a bay comprises a plurality of power lines, each of which comprising at least one switchgear apparatus. A line in this context should be understood to comprise a three phase conductor for electric power transmission, being it a cable or an over line arrangement.

The switchgear apparatus may comprise disconnectors and/or circuit breakers, each of which containing an electric power supported actuator. Each circuit breaker comprises a trigging device and a recovery device. The trigging device may comprise a solenoid, which by an electric pulse affects a latch for releasing the force of a pre-stressed spring equipment to move the contacts of the switchgear. The recovery device may comprise an electric rotating machine, which by electric power pre-stresses the spring equipment. The disconnector comprises an electric rotating machine effecting the relative movement of two contact parts between an open position and a closed position.

For controlling the substation the station is hierarchically divided into station level, bay level and process level. Each of these levels may comprise its own intelligence in the form of computer means controlled by a computer program. Commonly the substation control is conducted on station level. For some dedicated operations, however, the control may be performed on bay level and even at process level. Hence, the computer means may communicate with each other on the same level as well as between different levels. A galvanic connection on possess level must fulfill high demands of EMC immunity.

In high voltage substations it is known to arrange the electric power supply as a central power supply means comprising battery means. The battery means comprises a plurality of battery units. The battery means further comprises a charging device and maintenance equipment for supervising the performance of the battery units. It must be ensured that every battery unit has a potential of delivering a sufficient amount of electric power at all times. For redundant power supply it is known to arrange the battery means in pairs. Thus each battery means of such a pair must be capable of providing the full need of electric power of the whole substation. The power capacity is normally in the order of 400 Ah for delivery during a predetermined period of time.

The DC power means of a substation is commonly based upon free ventilated lead-acid batteries. Due to the fact that hydrogen is released during charging and hazardous electrolyte spillage must be held within control the normal design comprises a centralized DC-power means in a separate battery room common for the complete substation. For reasons of redundancy the battery room is organized with two sets of batteries. Each set of batteries comprises the full capacity of powering the whole substation. The battery room has to be equipped with special ventilation, hydrogen detectors and at least two evacuation rotes. Further the battery room must have a sufficient space to enable the handling of lead-acid batteries with trucks and must involve special containers to handle electrolytes.

The battery means has two distinct missions. On the one hand it must be capable of supplying high peaks of electric energy to the switchgear apparatus. For this mission the conductors transferring the electric power from the location of the battery room to the location of the actuator need to have a great cross section area. Such conductors comprise a high material cost that increases rapidly with distance. The conductors are also sensible for electromagnetic disturbances. On the other hand the battery means must be capable of supplying to the apparatus within the control system, such as computer means, a smooth electric power having no transients. It is known that at a high outtake of electric power for operating the switchgear apparatus may cause a decrease in the voltage level and thus disturb the power supply of the computer means.

The DC voltage is normally chosen relatively high. A voltage for powering the switchgear apparatus is often in the range of 110 to 220 V DC. The electric power is further transformed into lower values by DC/DC converters to suit the electronic control equipment. Such equipment may comprise internal DC/DC converters to further reduce the voltage. Due to an over-voltage situation during float-charge of lead-acid batteries all those DC/DC converters are subjected to heat stresses that sometimes cause malfunctions.

SUMMARY OF THE INVENTION

The present invention seeks to provide an improved power supply of an outdoor substation and a method of providing power supply at such a substation.

This is achieved according to the invention by a control apparatus characterized by the features in the independent claim 1 or by a method characterized by the steps in the independent claim 13. Preferred embodiments are described in the dependent claims.

According to the invention the power supply of the substation is decentralized. Each power consumer or cluster of consumers within the substation comprises their own power supply. A power consumer comprises a switchgear apparatus, a cluster of switchgear apparatus, computer means or a cluster of computer means. The power supply means thus are positioned closer to the power consumer, such as a switchgear apparatus. This arrangement makes possible the electric power conductors to be short. For redundant function the power supply means are arranged in pairs. According to the invention also the power supply of the computer means is decentralized such that each computer means comprises its own power supply means.

Further according to the invention the power supply means comprises a plurality of battery means to provide uninterruptible power supply. According to the invention these batteries comprises high energy density battery units that are environmentally safe. Such battery unit may comprise a Li-Ion battery. This kind of battery does not give away any flammable gases during charging. They are float charged to exact the chosen voltage level. This means that there will be no over- voltages. The Li-Ion battery has high specific energy content and thus has a small size. In comparison to a lead acid battery the Li-Ion battery comprises three times the energy for the same volume. In fact in comparison to a traditional battery room including all necessary equipment the equivalent space needed for an equivalent "Li-Ion battery room" would be just a fragment of the traditional battery room size. Hence by the expression high energy density in this context should be understood an energy density which is at least three times the energy density of a traditional lead acid battery. The Li-Ion battery may be placed openly with an arbitrary orientation and is suitable for operation between -35C to +60 C. The Li-Ion battery has no severe ageing and is regarded as "maintenance free".

By placing the battery means close to the usage a very robust and cost effective system is achieved. The battery means may be placed in a cupboard close to the "bay-house" or in direct connection to an individual apparatus. Each power supply means or redundant pair of power supply means comprises its own charger. For supervising and control each power supply means comprises an optic fiber connection to the control system. The switchgear apparatus and the control means at bay level may comprise separate power supply means.

Through a fiber connection: • the battery and battery charger self control will be monitored and alarm signals will be sent

• remote connections or disconnections of redundant battery strings is effected

• remote discharge test of a single battery string may be ordered • signals from the instrument transformers

• signals to circuit breaker to effect a close/open operation

In a first aspect of the invention the object is achieved by an outdoor substation for high voltage comprising at least one bay containing at least one power line with a plurality of switchgear apparatus, a control system and power supply means, wherein the power supply means is decentralized such that each bay comprises its own power supply. The bay may comprise one or a plurality of power lines, each comprising one or more switchgear apparatus. Thus, in one embodiment the power supply means comprises the power supply for the switchgear apparatus of one power line only. In another embodiment the power supply means comprises the power supply for the switchgear apparatus of a plurality of power lines. In this embodiment the power supply means comprises the capability of providing redundant power supply for the switchgear apparatus of a plurality of power lines.

In an embodiment of the invention the power supply means comprises battery means. In a further embodiment the battery means comprises high energy density battery units. The battery means comprises in one embodiment its own charging equipment. In a further embodiment the battery means comprises supervising means and communication means with the control system. In an embodiment the communication means comprises an optic fiber. For redundant power supply the battery means are in an embodiment organized in pairs capable of providing the full power supply for the switchgear apparatus of two power lines. In an embodiment of the invention the bay level control system comprises its own power supply system.

In a second aspect of the invention the object are achieved by a method for providing uninterrupted power supply of an outdoor substation for high voltage containing at least one bay with at least one power line comprising a plurality of switchgear apparatus, the method comprising: providing at each bay a local electric power supply means, providing the local electric power supply means to comprise battery means, arranging the battery means in pairs of battery units for redundant operation, providing each battery unit to comprise high energy density batteries.

The method further comprises providing a charger device for each local power supply means. The method also comprises the battery units being controlled and supervised by a computer means and the communication being effected through optic fibers.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will become more apparent to a person skilled in the art from the following detailed description in conjunction with the appended drawings in which:

Fig 1 is a principal circuit of a control apparatus according the invention, and

Fig 2 is a detail circuit of an embodiment of the invention. DESCRIPTION OF PREFERRED EMBODIMENTS

A substation 1 according to an embodiment of the invention as shown in fig 1 comprises an incoming line 2, a transformer 3 and a bay 4 containing three lines 5a, 5b, and 5c. Each line comprises a switching apparatus 6, a current transformer 7 and a voltage sensing means 8. The bay also contains control means 9 including computer means 10. Further the bay contains power supply means 11 containing a first battery unit 12 and a second battery unit 13 for redundant operation. The control means 9 supervises the switching apparatus of each line as indicated by the control conductor 14. The power means 11 with the two redundant battery units 12 and 13 comprise the power supply for the switching apparatus as indicated by the conductor 15. The power supply 11 in the embodiment shown also feed the control means 9 as indicated by the conductor 16.

The substation comprises an overall control system 17 containing a control computer means 18 and main power supply means 19. The main power supply means comprises in this embodiment a first 20 and second 21 control power supply battery unit for redundant power supply. The control system comprises a main ac power supply for feeding the distributed power supplies with charging capacity. One such ac feeding conductor 24 is connected to the bay power supply 11. The control system also supervises the total control of the substation. Thus for this purpose the substation comprises a plurality of data communication conductors. One such conductor is indicated in the embodiment the conductor 25. This conductor may comprise a galvanic conductor but comprises preferable an optic fiber for data communication. As indicated in the embodiment according to fig 1 the substation comprises a first 22 and second 23 circuit breaker on each side of the transformer 3. Also indicated with a circuit breaker symbol in the embodiment the switching apparatus 6 of each line 5a comprises at least one circuit breaker. However, depending on the switching need the switching apparatus may comprise further circuit breakers and disconnectors. These are all powered by the power supply means 11.

By providing the power supply at each bay the feeding conductors may be held short. This is advantageous since long conductors having the large cross section area needed results in heavy, high material demanding and costly power feeding lines. In the embodiment shown the power supply means 11 supply power to both the switching apparatus and the control means.

In a further embodiment of the invention represented by fig 2 the control means may comprise its own power supply 26.

Although favorable the scope of the invention must not be limited by the embodiment presented but contain also embodiments obvious to a person skilled in the art. For instance each line may comprise its own power supply means. Further each switching apparatus may comprise its own power supply.

Claims

1. An outdoor substation for high voltage comprising at least one bay containing at least one line including a switchgear apparatus, a control system and power supply means, c h a r a c t e r i z e d i n that the power supply means is decentralized such that each bay comprises its own power supply located in the bay.

2. An outdoor substation according to claim 1, wherein the bay comprises a plurality of power lines, each including at least one switchgear apparatus.

3. An outdoor substation according to claim 1 or 2, wherein the bay power supply means comprises the power supply for the switchgear apparatus of one line only.

4. An outdoor substation according to any of the preceding claims, wherein the bay power supply means comprises the power supply for the switchgear apparatus of a plurality of lines.

5. An outdoor substation according to any of the preceding claims, wherein the bay power supply means comprises the capability of providing redundant power supply for the switchgear apparatus of a plurality of lines.

6. An outdoor substation according to any of the preceding claims, wherein in one embodiment of the invention the power supply means comprises battery means.

7. An outdoor substation according to any of the preceding claims, wherein in a further embodiment the battery means comprises high energy density battery units.

8. An outdoor substation according to any of the preceding claims, wherein the battery means comprises in one embodiment it own charging equipment.

9. An outdoor substation according to any of the preceding claims, wherein in a further embodiment the battery means comprises supervising means and communication means with the control system.

10. An outdoor substation according to any of the preceding claims, wherein in an embodiment the communication means comprises an optic fiber.

11. An outdoor substation according to any of the preceding claims, wherein for redundant power supply the battery means are organized in pairs capable of providing the full power supply for the switchgear apparatus of two power lines.

12. An outdoor substation according to any of the preceding claims, wherein in an embodiment of the invention the bay level control system comprises its own power supply system.

13. A method for providing uninterrupted power supply of an outdoor substation for high voltage containing at least one bay with at least one power line comprising a plurality of switchgear apparatus, the method c h a r a c t e r i z e d b y : providing at each bay a local electric power supply means, providing the local power supply means to comprise battery means, arranging the battery means in pairs of battery units for redundant operation, and providing the battery units to comprise high energy density batteries.

14. A method according to claim 13, wherein the method further comprises providing a charger device for each local power supply means.

15. A method according to claim 13, wherein the method also comprises the battery units being controlled and supervised by a computer means and the communication being effected through optic fibers.

16. Computer program product storable on a computer usable medium containing instructions for a processor to evaluate the method of claim 10 to 12.

17. Computer program product according to claims 16 provided at least in part over a network, such as the Internet.

18. Computer readable medium, characterized in that it contains a computer program product according to claim 16.