Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
  • G01R35/00—Testing or calibrating of apparatus covered by the other groups of this subclass
  • G01R35/04—Testing or calibrating of apparatus covered by the other groups of this subclass of instruments for measuring time integral of power or current

Definitions

• the present invention relates to checking systems for control measurement of energy measuring systems, more specifically to checking systems for control measurement, carried out in the field, of energy measuring systems operating in high-voltage environment.
• Energy measuring systems operating in high-voltage environments are installed by a power distributor in distribution plants or with customers connected to the high-voltage network of the power distributor (network owner) .
• the energy measuring system measures the energy taken from the high-voltage network.
• the usual procedure is to go to the energy measuring system, disconnect the high-voltage network, dismount the measuring transformer, take it to a checking laboratory and there connect it to a high-voltage-generating plant in the same manner as it is connected in the field.
• a laboratory measuring transformer that is used for check ⁇ ing voltage and current is very exact.
• On the secondary side of the current or voltage measuring transformer absolute values are measured, and a correction number, or error of measurement, is determined.
• the normal measuring transformer should be able to handle the high-voltages in the high-voltage network with very great accuracy, which means that it must be made very large and heavy. In order to illustrate its size, it may be mentioned that it has a length of 5 m and weighs 1.5 tonnes. It is also disadvantageous that the checking system is dependent on the high-voltage net ⁇ work. One more drawback of this checking system is that it is only designed for checking of one voltage transfor ⁇ mer at a time.
• One object of the present invention is to provide a mobile checking system, by which the total errors of an energy measuring system can be determined.
• a further object of the present invention is to provide a checking system which is not dependent on the high-voltage network.
• the high-voltage- and heavy-current-generating means contribute to the mobility of the checking system by mak ⁇ ing the system independent of the high-voltage network, which permits, among other things, normal-current- and normal-voltage-generating means which are considerably smaller than the above-mentioned prior-art normal trans ⁇ former which is actually mobile. This is due to the fact that it is not necessary to consider the strict operating requirements that are placed on equipment that is to ope ⁇ rate in the network.
• FIG. 1 shows in a block diagram a checking system according to an embodiment of the present invention.
• Fig. 2 shows the system in Fig. 1 in more detail. Detailed Description of the Preferred Embodiment
• Fig. 1 is a block diagram of a checking system according to a preferred embodiment of the present inven ⁇ tion.
• the checking system comprises the units which have the reference numeral 1 and are framed by a dash-dotted line.
• the checking system 1 is shown connected to an energy measuring system 2.
• the energy measuring system comprises the units having the reference numeral 2 and being framed by a dash-dotted line.
• the checking system comprises a power supply unit 3, a current combining means 6, a voltage combining means 7, a comparator unit or normal comparator 8, and a control ⁇ ling and regulating unit 9.
• the energy measuring system 2 comprises a current detecting unit 21, a voltage detect- ing unit 22 and an energy measuring unit 23.
• the current detecting and voltage detecting units 21, 22 are con ⁇ nected to a high-voltage network, from which they can be separated by means of a separator 24.
• a plant such as a distribution plant, is, at 26, connected to the end of the lines 25 of the high-voltage network.
• the checking system 1 is mobile and is preferably arranged in a vehicle, such as a bus, with a trailer. It will be explained in more detail below how this mobility is achieved.
• the checking system 1 is sup- plied via some external supply other than the high-vol ⁇ tage network, such as a portable power plant or an AC distribution box. This external supply is connected at 10.
• the power supply unit 3 is connected to the current combining means 6, which in turn is connected to the nor- mal comparator 8 and an outlet 11.
• the current detecting unit 21 of the energy measuring system 2 is connected to the outlet 11.
• the power supply unit 3 is further connected to the voltage combining means 7, which in turn is connect- ed to the normal comparator 8 and an outlet 12.
• the vol ⁇ tage detecting unit 22 of the energy measuring system 2 is connected to the outlet 12.
• the checking system 1 has one more interface towards the energy measuring system, viz. between the normal com- parator 8 and the energy measuring unit 23.
• the energy measuring unit 23 has an optical outlet 27 and/or a con ⁇ tact outlet 28. This/these emits/emit pulses at a fre- quency which is proportional to the energy consumption measured by the energy measuring unit 23.
• the outlet/out ⁇ lets 27 and/or 28 of the energy measuring unit 23 thus is/are connected to the normal comparator 8.
• the control- ling and regulating unit 9 is connected to the normal comparator 8 for collecting measured values from this, and to the power supply unit 3 for determining the fre ⁇ quency of the current and the voltage leaving the power supply unit.
• the controlling and regulating unit thus regulates the current and the voltage leaving the power supply unit 3, the feedback consisting of the measured values from the normal comparator.
• the checking system 1 operates in 3-phase (three currents and three voltages). This should be seen as an example only. Other system variants, e.g. three currents and two voltages are, of course, possible within the scope of the invention.
• the checking system 1 briefly functions as follows.
• the power supply unit 3 generates current in three phases and supplies this to the current combining means 6.
• the current combining means 6 generates heavy current (in three phases) , of the same magnitude as the current in the high-voltage network, at very low voltage and sup ⁇ plies this heavy current to the current detecting unit 21.
• the current combining means 6 also generates a refe ⁇ rence or normal current and supplies this to the normal comparator 8.
• the current is stepped down in the current detecting unit 21 and supplied to the energy measuring unit 23.
• the power supply unit 3 also generates voltage in three phases and supplies this voltage to the voltage combining means 7.
• the voltage combining means 7 gene ⁇ rates high voltage (in three phases) of the same magni ⁇ tude as the voltage in the high-voltage network, at very low current, and supplies this high voltage to the vol ⁇ tage detecting unit 22.
• the voltage combining means 7 also generates a reference or normal voltage and supplies this to the normal comparator 8.
• the voltage detecting unit 22 steps the voltage down and supplies the stepped- down voltage to the energy measuring unit 23.
• the energy measuring unit 23 measures the power flow.
• the normal comparator 8 determines a reference or normal power flow and compares this with the correspond ⁇ ing value collected from the optical outlet 27 of the energy measuring unit 23. The difference then detected by the normal comparator is a measure of the total error of measurement in the energy measuring system 2.
• the controlling and regulating unit 9 which here is a PC, is used to control and regulate the checking system, which comprises the step of controlling, via the power supply unit 3, the phase relation, frequency and amplitude of the currents and voltages.
• the checking system 1 according to the invention will now be described in more detail with reference to Fig. 2.
• the power supply unit 3 comprises a current gene ⁇ rator 4, a voltage generator 5, a power pack 41, which is connected to the external power source and to the current and voltage generators and which supplies direct voltages to each generator 4, 5, and a first 42 and second 43 function generator which generates and supplies to the current generator 4 and the voltage generator 5, respec- tively, signals for controlling frequency and amplitude of the currents and voltages generated by the generators 4, 5 and for controlling the mutual phases between the currents and between the voltages.
• the current combining means 6 has three inlets, one for each phase. To each inlet are connected two conduc ⁇ tors 44, 45; 46, 47; 48, 49 from the generator 4. The conductors 44, 45; 46, 47; 48, 49 are connected to the primary side of transformers 50-52 for stepping up the currents supplied from the current generator 4.
• the secondary side of each transformer 50-52 has two connec ⁇ tions 53, 54; 55, 56; 57, 58 which are connected to the primary side of a measuring transformer 59, 60, 61 in the current detecting unit 21. Between one connection 54, 56, 58 of each transformer and the measuring transformer 59-61, a normal transformer 62, 63, 64 is connected.
• each measuring transformer 59-61 steps down the current and supplies it to the energy meter or Wh meter 23, to which the secondary side of the measuring transformer 59, 60, 61 is connected.
• the normal transformers 62-64 step down the currents by essentially the same transformation factor and then supply them to a normal meter 65 in the comparator unit 8.
• the current transformers 50-52 for stepping up are designed in such manner that they generate in their secondary windings great currents, for instance 600 A or 1200 A, while the voltage drop across the secondary wind ⁇ ings is extremely low, a few volts. This results in the power development in the transformers 50-52 being very low and thus the possibility of making the transformers 50-52 relatively small. This is necessary for the mobi ⁇ lity and the requirement that the connection cables for the great currents be short (about a meter) .
• the voltage combining means 7 comprises three trans ⁇ formers 66-68 for stepping up the voltages supplied by the voltage generator to high-voltage levels, such as 20 kV or 130 kV, and three normal transformers 69-71.
• Each of the transformers 66-68 is connected to a measur ⁇ ing transformer 72-74 for voltage detection.
• Each measur ⁇ ing transformer 72-74 steps down the voltage and supplies it to the energy meter 23.
• Each normal transformer 69, 70 or 71 is connected to the secondary side of one of the transformers 66, 67 or 68 and steps down the voltage by essentially the same transformation factor as the measur ⁇ ing transformers so as then to supply the voltage to the normal meter 65.
• the transformers 66-68 are designed such that they generate the high voltage at low current, for instance some twenty or thirty milliamperes. They are of a relatively seen small size, which is possible owing to the low power they need to cope with and owing to the fact that they need not be designed in the same manner as the operating transformers.
• a value is determined, which in the following is called normal value, of the inlet ener ⁇ gy.
• the normal value is supplied to a comparator circuit 75 in the comparator unit 8.
• the energy meter 23 deter ⁇ mines a corresponding value, below called measured value, that applies to the energy measuring system 2.
• the mea ⁇ sured value is supplied to the comparator circuit 75 via the optical outlet 27 and is there compared with the nor ⁇ mal value. The difference constitutes the total error of measurement in the entire energy measuring system 2. This total error cannot be determined by conventional measur ⁇ ing methods.
• the system 1 may also be used for checking each of the measuring transformers 59-61, 72-74, the comparator unit 8 having inlets arrang- ed for the purpose.
• the inventive checking system is mobile. More spe ⁇ cifically, it is arranged in a vehicle, preferably a bus with a trailer.
• the high-voltage transformers are arrang ⁇ ed on the trailer, and the rest of the system 1 is ar- ranged in the bus, which means that only short cables between the trailer and the bus are required for trans ⁇ mitting the low voltages and currents.
• the distances between the transformers 50-52; 66-68 and the normal transformers 62-64; 69-71 are short.
• the new ways of thinking according to the invention and the unique design of the system as described above have yielded com ⁇ ponents of such a small size that the entire system can be accommodated in a bus with trailer. Consequently the entire system will be extremely mobile.
• An advantage of the inventive checking is that it involves an immediate comparison and is not based on the necessity of determining an absolute value. It is there ⁇ fore not critical if the currents and voltages supplied to the measuring transformers 59-61; 72-74 vary somewhat in time since the variations are reflected both in the energy measuring system 2 and in the checking system 1.
• a further important advantage is that the stepping-up transformers included in the checking system need not be of the same size in terms of power as the stepping-up transformers used in prior art when checking individual measuring transformers in the laboratory, which means that they can be made considerably smaller.
• the checking sys- tern 1 does not require access to the high-voltage net ⁇ work, but is supplied by another source, preferably a fuel-powered, portable power plant. Consequently, the load ratio on the network is not interfered with by the checking and vice versa. Moreover, a difficult connection to the high-voltage network is avoided (short-circuit effects etc. ). Further the normal transformers operate under controlled conditions in each measurement, which means that one is well acquainted with the any ratio er ⁇ rors of the normal transformers and other values that vary with the supplied current/voltage and the environ ⁇ ment.
• connection to another power source than the high-voltage network also confers the advantage that the dimensions of the normal transformers can be sig- nificantly reduced in relation to the above-mentioned prior-art mobile normal transformer.
• the reason for this is that the requirements for insulation properties as well as other properties to make the transformer cope with the operation conditions and the safety in the high- voltage network do not exist.
• the PC is an important utensil to make the measure ⁇ ment rational and to rapidly perform any correction cal ⁇ culations and account for the measurement result.

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Remote Monitoring And Control Of Power-Distribution Networks (AREA)
• Measurement Of Current Or Voltage (AREA)
• Spray Control Apparatus (AREA)
• Flow Control (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=20399987

Family Applications (1)

Country Status (5)

Cited By (1)

Families Citing this family (9)

Family Cites Families (1)

• 1995
  • 1995-10-27 SE SE9503787A patent/SE9503787L/sv not_active IP Right Cessation
• 1996
  • 1996-10-26 AU AU73569/96A patent/AU7356996A/en not_active Abandoned
  • 1996-10-26 EP EP96935762A patent/EP0857294A1/en not_active Ceased
  • 1996-10-26 WO PCT/SE1996/001378 patent/WO1997015806A1/en not_active Application Discontinuation
• 1998
  • 1998-04-22 NO NO19981786A patent/NO324345B1/no not_active IP Right Cessation

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events