CA1246671A - Power take-off from transformer tap changer winding - Google Patents
Power take-off from transformer tap changer windingInfo
- Publication number
- CA1246671A CA1246671A CA000461627A CA461627A CA1246671A CA 1246671 A CA1246671 A CA 1246671A CA 000461627 A CA000461627 A CA 000461627A CA 461627 A CA461627 A CA 461627A CA 1246671 A CA1246671 A CA 1246671A
- Authority
- CA
- Canada
- Prior art keywords
- winding
- power
- transformer
- tap changer
- take
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
- H02M5/02—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc
- H02M5/04—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters
- H02M5/10—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using transformers
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Housings And Mounting Of Transformers (AREA)
Abstract
POWER TAKE-OFF FROM TRANSFORMER TAP CHANGER WINDING
ABSTRACT OF THE DISCLOSURE
A power system may have one or more stations which have a need for electrical power to service the station. Such a power station has at least one large power transformer with a tap changer winding to accommodate changes in demand for power. In the past a separate service winding was added to the power transformer to provide the take-off power for the station. The service winding had a low impedance and under fault conditions tended to carry high current.
This required a mechanically stronger core and windings, and a heavier connection with the service winding. In the invention, instead of a separate service winding, an auxiliary transformer having two windings is provided. One winding is connected in parallel with the tap changer winding. The other winding provides take-off power for the station.
Because the tap changer winding has a higher impedance than a service winding, it tends to carry a smaller current under fault conditions making it possible to use a smaller core and smaller connections for the power take-off.
ABSTRACT OF THE DISCLOSURE
A power system may have one or more stations which have a need for electrical power to service the station. Such a power station has at least one large power transformer with a tap changer winding to accommodate changes in demand for power. In the past a separate service winding was added to the power transformer to provide the take-off power for the station. The service winding had a low impedance and under fault conditions tended to carry high current.
This required a mechanically stronger core and windings, and a heavier connection with the service winding. In the invention, instead of a separate service winding, an auxiliary transformer having two windings is provided. One winding is connected in parallel with the tap changer winding. The other winding provides take-off power for the station.
Because the tap changer winding has a higher impedance than a service winding, it tends to carry a smaller current under fault conditions making it possible to use a smaller core and smaller connections for the power take-off.
Description
. -i7~
Case 2879 POWER TAKE~OFF FROM TRANSFORMER TAP CHANGER WINDING
This invention relates to a power take-off from a transformer, and in particular it relates to a power take-off from a tap changer winding.
A power system normally has a plurality of power stations to control or regulate the power transferred over the power system according to the demand. Each power statio~ normally has at least one large transformer where one of the windinys includes a tap changer winding to alter the voltage in discrete steps. It is common practice to add a service winding to a large transformer at a power station to provide electrical power for use at the station. The power transformer for the station is normally only a small fraction of the main power transformer rating. For one example only, a Iarge power transformer at a power station might be of the order of 135 MVA whereas the service power requirement of the station may be of the order of one MVA or perhaps less.
It is relatively expensive to add a separate service winding to a large power transformer. The inherent impedance characteristics of such a winding tend to be low and under fault conditions the current in the service winding tends to be temporarily high.
Therefore high mechanical forces are generated in the service windiny and the winding must be made ,~"
6~
Case 2879 mechanically strong to resist these orces. The mechanical strength is achieved by using more material or using high strength material, or both. Tbis tends to increase the cost of the transformer as well as its size.
In addition, because the fault currents in such a prior art arrangement tend to be high, special attention must be given to the external connections to the service windingL It is common to use bus duct for these external connections to protect against short circuit currents, and bus duct tends to further increase the cost.
In accordance with the present invention, connections are made to the tap changer winding which is available on the power transformer. r~his arrangement does not require the additional service winding. The connections from the tap changer winding go to an auxiliary transformer which is separate from the main windings and which provides the desired voltage. This arrangement requires a small increase in the tap changer winding and it eliminates the need for a service winding on the power transformer. It does require an auxiliary transformer but the cost of this is considerably less than the cost of the service winding with its added material and greater transformer size.
The tap changer winding has inherently impedance characteristics much higher than those of the service winding previously discussed. This is desirable as it limits the current in the winding which occurs as the result of a fault. This reduces the level of mechanical forces in all the windings which result from short circuit faults. Consequently the tap chanyer winding need not be increased in size when it services the dual purpose of this invention, other than to provide for a small fraction of extra power.~ That is, the fault induced currents are of no .
,, , , 73~
Case 2879 greater magnitude than in a prior art~ single purpose, tap changer winding. In additionl because the fault currents induced in the tap changer winding are not unduly high (they are very much less than in a separate service winding~, the external connections to carry out the power for the station do not require special precautions. It is not necessary to use bus duct so the external connections are simpler.
It is therefore a feature of the invention to provide a power take-off from the tap changer winding of a transformer.
It is another feature of the invention to provide a power take-off for the power require~ents of a power station that does not require a separate service winding on a power transformer.
Accordingly there is provided a power take-off in a transformer having a first winding, a second winding and a tap changer winding connected with said first winding, comprising an auxiliary transformer portion having third and fourth windings, said third winding being connected in parallel to said tap changer winding, and said fourtb winding providing take-off power.
The invention will be described with reference to the drawings in which, Figure 1 is a schematic diagram of a prior art arrangement of a power transformer having a service winding, and Figure 2 is a schematic diagram of a power take-off arrangement according to the invention.
Re~erring to Figure 1 there is shown a prior art power transformer, in schematic form, having a core 10, a service winding 11 and a secondary winding 12. A primary winding 14 has a tap chanqer winding 15 with a switch 16 for connecting the winding in either an adding or a subtracting configuration as is known.
:
,~ .
~6Ç;7~
Case 2879 The windiny 15 has a plurality of tap contacts 17 and a moving contact 18 can be positioned to engaye any one of the contactsO
The terminals of the service winding 11 are designated Zl and Z2~ The terminals of winding 12 are designated Xl and X2, and the terminals of the primary winding including the tap changer windiny are designated Hl and H2.
Referring now to Figure 2, there is shown a schematic diagram of an arrangement according to the invention where a core 10' has a secondary windin~
and a primary winding 14' including a tap changer winding 15'. A switch 16' is included for changing the configuration of winding 15'. The tap contacts lS 17' are on winding 15'. T~is is yuite similar to Figure 1 and like parts have been given the same designation number with a primed symbol added. The only difference so far is the absence in Figure 2 of a service winding. The terminals have also been given the same designations with a primed symbol.
Still referring to Figure 2, two conductors or connectors 20 and 21 connect the ends of tap changer winding 15' to a winding 22 of an auxiliary transformer 23 having a core 24. The core 24 is separate from core 10'. An output winding 25 on core 24 has terminals Z3 and Z4.
The main unit 26 may be considered to comprise core 10' with windings 12', 14' and 15', including switcb 16', taps 17' and movable contact 18', This is indicated as the part to the left of broken line 27 in Figure 2. In the actual construction of a power transformer, the main unit 26 and the auxiliary unit 23 would normally be mounted in the same transformer t~nk, In other words the power transformer arrangement of ~igure 2 would have on it :terminals Xl, X2, Hl~ H2l 3 4 There would, of course, also be controls for switch Case 2879 16' and movable contact 18'. It is, oE course~ not necessary that the main and auxiliary units be in the same transformer tanks.
It is believed that the preceding description will provide an understanding of the invention and that other variations will occur to those skilled in the art.
Case 2879 POWER TAKE~OFF FROM TRANSFORMER TAP CHANGER WINDING
This invention relates to a power take-off from a transformer, and in particular it relates to a power take-off from a tap changer winding.
A power system normally has a plurality of power stations to control or regulate the power transferred over the power system according to the demand. Each power statio~ normally has at least one large transformer where one of the windinys includes a tap changer winding to alter the voltage in discrete steps. It is common practice to add a service winding to a large transformer at a power station to provide electrical power for use at the station. The power transformer for the station is normally only a small fraction of the main power transformer rating. For one example only, a Iarge power transformer at a power station might be of the order of 135 MVA whereas the service power requirement of the station may be of the order of one MVA or perhaps less.
It is relatively expensive to add a separate service winding to a large power transformer. The inherent impedance characteristics of such a winding tend to be low and under fault conditions the current in the service winding tends to be temporarily high.
Therefore high mechanical forces are generated in the service windiny and the winding must be made ,~"
6~
Case 2879 mechanically strong to resist these orces. The mechanical strength is achieved by using more material or using high strength material, or both. Tbis tends to increase the cost of the transformer as well as its size.
In addition, because the fault currents in such a prior art arrangement tend to be high, special attention must be given to the external connections to the service windingL It is common to use bus duct for these external connections to protect against short circuit currents, and bus duct tends to further increase the cost.
In accordance with the present invention, connections are made to the tap changer winding which is available on the power transformer. r~his arrangement does not require the additional service winding. The connections from the tap changer winding go to an auxiliary transformer which is separate from the main windings and which provides the desired voltage. This arrangement requires a small increase in the tap changer winding and it eliminates the need for a service winding on the power transformer. It does require an auxiliary transformer but the cost of this is considerably less than the cost of the service winding with its added material and greater transformer size.
The tap changer winding has inherently impedance characteristics much higher than those of the service winding previously discussed. This is desirable as it limits the current in the winding which occurs as the result of a fault. This reduces the level of mechanical forces in all the windings which result from short circuit faults. Consequently the tap chanyer winding need not be increased in size when it services the dual purpose of this invention, other than to provide for a small fraction of extra power.~ That is, the fault induced currents are of no .
,, , , 73~
Case 2879 greater magnitude than in a prior art~ single purpose, tap changer winding. In additionl because the fault currents induced in the tap changer winding are not unduly high (they are very much less than in a separate service winding~, the external connections to carry out the power for the station do not require special precautions. It is not necessary to use bus duct so the external connections are simpler.
It is therefore a feature of the invention to provide a power take-off from the tap changer winding of a transformer.
It is another feature of the invention to provide a power take-off for the power require~ents of a power station that does not require a separate service winding on a power transformer.
Accordingly there is provided a power take-off in a transformer having a first winding, a second winding and a tap changer winding connected with said first winding, comprising an auxiliary transformer portion having third and fourth windings, said third winding being connected in parallel to said tap changer winding, and said fourtb winding providing take-off power.
The invention will be described with reference to the drawings in which, Figure 1 is a schematic diagram of a prior art arrangement of a power transformer having a service winding, and Figure 2 is a schematic diagram of a power take-off arrangement according to the invention.
Re~erring to Figure 1 there is shown a prior art power transformer, in schematic form, having a core 10, a service winding 11 and a secondary winding 12. A primary winding 14 has a tap chanqer winding 15 with a switch 16 for connecting the winding in either an adding or a subtracting configuration as is known.
:
,~ .
~6Ç;7~
Case 2879 The windiny 15 has a plurality of tap contacts 17 and a moving contact 18 can be positioned to engaye any one of the contactsO
The terminals of the service winding 11 are designated Zl and Z2~ The terminals of winding 12 are designated Xl and X2, and the terminals of the primary winding including the tap changer windiny are designated Hl and H2.
Referring now to Figure 2, there is shown a schematic diagram of an arrangement according to the invention where a core 10' has a secondary windin~
and a primary winding 14' including a tap changer winding 15'. A switch 16' is included for changing the configuration of winding 15'. The tap contacts lS 17' are on winding 15'. T~is is yuite similar to Figure 1 and like parts have been given the same designation number with a primed symbol added. The only difference so far is the absence in Figure 2 of a service winding. The terminals have also been given the same designations with a primed symbol.
Still referring to Figure 2, two conductors or connectors 20 and 21 connect the ends of tap changer winding 15' to a winding 22 of an auxiliary transformer 23 having a core 24. The core 24 is separate from core 10'. An output winding 25 on core 24 has terminals Z3 and Z4.
The main unit 26 may be considered to comprise core 10' with windings 12', 14' and 15', including switcb 16', taps 17' and movable contact 18', This is indicated as the part to the left of broken line 27 in Figure 2. In the actual construction of a power transformer, the main unit 26 and the auxiliary unit 23 would normally be mounted in the same transformer t~nk, In other words the power transformer arrangement of ~igure 2 would have on it :terminals Xl, X2, Hl~ H2l 3 4 There would, of course, also be controls for switch Case 2879 16' and movable contact 18'. It is, oE course~ not necessary that the main and auxiliary units be in the same transformer tanks.
It is believed that the preceding description will provide an understanding of the invention and that other variations will occur to those skilled in the art.
Claims (4)
1. A power take-off in a transformer having a first winding, a second winding and a tap changer winding connected with said first winding, comprising an auxiliary transformer portion having third and fourth windings, said third winding being connected in parallel to said tap changer winding, and said fourth winding providing take-off power.
2. In a power station having a transformer with at least a first winding, a second winding and a tap changer winding connected with said first winding all on a main core, a power take-off arrangement comprising an auxiliary transformer having third and fourth windings on an auxiliary core, said third winding being connected in parallel with said tap changer winding and said fourth winding providing a take-off for electrical power for said power station.
3. A power station according to claim 2 in which said transformer and said auxiliary transformer are mounted in a common transformer tank.
4. A power take-off arrangement comprising a large transformer having a main core, a primary and second winding and a tap changer winding on said main core, said tap changer winding having a series connection with one end of said primary winding, a plurality of tap contacts on said tap changer winding and a movable contact for making contact with selected ones of said plurality of tap contacts to provide a variable voltage between the other end of said primary winding and said movable contact, and an auxiliary core having an input and an output winding, said input winding being connected in parallel with said tap changer windings, and saidoutput winding providing the take-off power.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000461627A CA1246671A (en) | 1984-08-23 | 1984-08-23 | Power take-off from transformer tap changer winding |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000461627A CA1246671A (en) | 1984-08-23 | 1984-08-23 | Power take-off from transformer tap changer winding |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1246671A true CA1246671A (en) | 1988-12-13 |
Family
ID=4128572
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000461627A Expired CA1246671A (en) | 1984-08-23 | 1984-08-23 | Power take-off from transformer tap changer winding |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1246671A (en) |
-
1984
- 1984-08-23 CA CA000461627A patent/CA1246671A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |