GB2239955A - A high voltage voltmeter - Google Patents
A high voltage voltmeter Download PDFInfo
- Publication number
- GB2239955A GB2239955A GB9000594A GB9000594A GB2239955A GB 2239955 A GB2239955 A GB 2239955A GB 9000594 A GB9000594 A GB 9000594A GB 9000594 A GB9000594 A GB 9000594A GB 2239955 A GB2239955 A GB 2239955A
- Authority
- GB
- United Kingdom
- Prior art keywords
- high voltage
- electrode
- electrodes
- voltmeter
- voltage voltmeter
- 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.)
- Withdrawn
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R5/00—Instruments for converting a single current or a single voltage into a mechanical displacement
- G01R5/28—Electrostatic instruments
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/144—Measuring arrangements for voltage not covered by other subgroups of G01R15/14
Abstract
A high voltage voltmeter which operates by measuring the electrostatic attraction between two electrodes when a voltage is applied, comprises a high voltage electrode 1, an earth electrode 2 and a guard electrode 3. The attractive force experienced by the earth electrode 2 is measured by a measuring means 4, e.g. incorporating a strain gauge. and this gives an electrical signal indicative of the applied voltage. The electrodes 1, 2 and 3 are surrounded either with a dielectric gas. e.g. sulphur hexafluoride or a vacuum. <IMAGE>
Description
A HIGH VOLTAGE VOLTMETER
This invention relates to a -high voltage voltmeter for measuring high voltage
Requirements have arisen from of power distribution companies for more accurate metering of the distributed power. For this to be possible, the voltage must be measured to a greater accuracy than currently possible with conventional meters.
Further, workers in high voltage laboratories require means for measuring voltages more accurately than currently available.
The electrostatic type of voltmeter offers the advantage of simplicity. However, difficulties associated with traditional electrostatic voltmeters have arisen because of the delicate nature of the mechanism needed to amplify movement caused by electrostatic attraction of the electrodes and the size of the instrument which is governed by the need for electrical clearances sufficient to sustain high voltages and prevent arcing or tracking.
Accordingly, the present invention provides a high voltage voltmeter comprising an earth electrode; high voltage electrode electrically insulated from said earth electrode; and a load measuring means; wherein said electrodes are juxtaposed so as to be urged together when a voltage is applied across them, and at least one of said electrodes is mechanically coupled to said load measuring means so that said load measuring means provides an indication of said applied voltage.
Preferably, said electrodes are planar and substantially parallel.
Further, to accurately define the electric field between the electrodes, the present invention preferably includes a guard electrode substantially surrounding and co planar with said one electrode and wherein the other said electrode is larger than said one electrode, so as to be juxtaposed about its periphery to said guard electrode.
In preferred embodiments, the load measuring means comprises a strain sensor which is preferably a strain gauge. The electrodes may be surrounded either by a vacuum or by a dielectric which may be sulphur hexaflouride.
This invention has advantages over conventional high voltage voltmeters in that it is a compact, robust and much more sensitive instrument.
An example of the present invention will now be described with reference to the accompanying drawings, in which;
Figure 1 is a cross section through the high voltage voltmeter embodying the invention, and Fissure 2 is a perspective view of the high voltage voltmeter of figure 1.
Referring now to the drawings, a high voltage electrode 1, in the shape of a disk, is positioned adjacent to and parallel with an earth electrode 2.
The earth electrode 2 is also of disk shape, but of smaller diameter, and is mechanically coupled to a load measuring means 4. Surrounding the periphery of the earth electrode 2, is a guard electrode 3.
The high voltage electrode 1 is held by a connector 9 in a fixed position such that its face 5 is parallel to the face 6 of the earth electrode 2. The connector 9 also serves to provide for electrical connection to a voltage source when the high voltage voltmeter is in use.
The electrodes 1, 2 and 3 can be constructed from durable electrically conducting material which is preferably a metal such as aluminium, copper or stainless steel.
Surrounding the electrodes 1, 2 and 3 and preventing arcing between the electrodes 1, 2 and 3, is either an electro-negative gas such as sulphur hexaflouride (SF6) or a vacuum. With improvements in modern vacuum technology, it is possible to encapsulate the electrodes 1, 2 and 3 and provide a sufficiently good vacuum, such that arcing is prevented. In the alternative configuration, when the electrodes 1, 2 and 3 are encapsuled in a medium of SF6 gas, the gas would preferably be at a pressure of about 3 bar.
The load measuring means 4 comprises a strain sensor which can for example be a strain gauge. The strain sensor is mechanically coupled to the earth electrode 2 and will provide an electrical signal indicative of the force on the earth electrode 2.
In operation, the earth electrode 2 is connected to the common earth of a voltage supply and a high voltage is applied across the electrodes 1 and 2.
This high voltage will cause the earth electrode 2 to be electrostatically attracted towards the high voltage electrode 1. The electric field produced by this voltage is well-defined in the electrode gap 8, since the face 7 of the earth guard electrode 3 maintains the electric field density constant between the earth electrode 2 and the high voltage electrode 1 and prevents the earth electrode 2 from experiencing any edge effects.
The electrode gap 8 between the electrodes 1 and 2 will remain effectively constant, the load measuring means 4 will not allow significant displacement of the earth electrode 2, but will measure the strain induced by the attractive force experienced by the earth electrode 2. The gap 8 between the electrodes 1 and 2 does not change significantly, and hence the force experienced by the earth electrode 2 does not vary significantly.
For maximum accuracy, the apparatus should be operated in an upright position to minimise "off centre" forces.
The attractive force between the high voltage electrode 1 and the earth electrode 2 can be expressed as;
NEWTON where E is the dielectric constant, a is the area of the earth electrode, V is the voltage, and S is the electrode gap.
For an applied voltage of 100 kV, an earth electrode 2 diameter of 10 cm, an electrode gap 8 of 1 cm with a vacuum separating the electrodes, the force experienced by the earth electrode 2 would be 347.54 x 10 Newtons, or 354.3 grams.
It can be seen from the above equation, the high voltage voltmeter can be calibrated from first principals, and need not be calibrated using a reference voltmeter.
The apparatus can measure not only DC voltage, but also AC voltage and will provide a measure of the
Root Mean Square (RMS) of the voltage amplitude.
When measuring AC voltage, the apparatus acts as a rectifier and the force between the electrodes 1 and 2 is always attractive, the force being indicative of the RMS of the voltage.
Further, when measuring AC voltage, information on phase angle may be obtained by connecting the load measuring means 4 or the earth guard electrode 2 to earth through a capacitor of significantly greater capacitance than that existing between the high voltage electrode 1 and the earth electrode 2 or guard electrode 3 repectively.
Claims (11)
1. A high voltage voltmeter comprising an earth electrode; high voltage electrode electrically insulated from said earth electrode; and a load measuring means; wherein said electrodes are juxtaposed so as to be urged together when a voltage is applied across them, and at least one of said electrodes is mechanically coupled to said load measuring means so that said load measuring means provides an indication of said applied voltage.
2. A high voltage voltmeter as claimed in Claim 1 wherein said electrodes are planar and substantially parallel.
3. A high voltage voltmeter as claimed in claim 2 and further including guard electrode substantially surrounding and coplanar with said one electrode and, wherein the other said electrode is larger than said one electrode, so as to be juxtaposed about its periphery to said guard electrode.
4. A high voltage voltmeter as claimed in claim 2 or claim 3 wherein said planar electrodes are circular.
5. A high voltage voltmeter as claimed in any preceding claim wherein said load measuring means comprises a strain sensor.
6. A high voltage voltmeter as claimed in claim 5 wherein said strain sensor comprises a strain gauge.
7. A high voltage voltmeter as claimed in any preceding claim wherein said electrodes are surrounded by a dielectric.
8. A high voltage voltmeter as claimed in claim 7 wherein said dielectric comprises an electro negative gas.
9. A high voltage voltmeter as claimed in claim 8 wherein said electro negative gas comprises sulphur hexaflouride.
10. A high voltage voltmeter as claimed in any of claims 1 to 6 wherein said electrodes are in a vacuum.
11. A high voltage voltmeter substantially as herein before described with reference to and as illustrated by the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9000594A GB2239955A (en) | 1990-01-11 | 1990-01-11 | A high voltage voltmeter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9000594A GB2239955A (en) | 1990-01-11 | 1990-01-11 | A high voltage voltmeter |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB9000594D0 GB9000594D0 (en) | 1990-03-14 |
| GB2239955A true GB2239955A (en) | 1991-07-17 |
Family
ID=10669117
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9000594A Withdrawn GB2239955A (en) | 1990-01-11 | 1990-01-11 | A high voltage voltmeter |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2239955A (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB544630A (en) * | 1941-09-09 | 1942-04-21 | Pantaleon Lenkchevitch | Improvements in weighing balances |
| GB2157838A (en) * | 1984-04-13 | 1985-10-30 | Xerox Corp | Electrostatic voltmeter |
-
1990
- 1990-01-11 GB GB9000594A patent/GB2239955A/en not_active Withdrawn
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB544630A (en) * | 1941-09-09 | 1942-04-21 | Pantaleon Lenkchevitch | Improvements in weighing balances |
| GB2157838A (en) * | 1984-04-13 | 1985-10-30 | Xerox Corp | Electrostatic voltmeter |
Non-Patent Citations (4)
| Title |
|---|
| "Electricity and Magnetism",B.I.Bleaney and B.Bleaney,pages 31,32(The attracted disc electrometer) * |
| electrometers),Pitman Press (Pitman paperbacks) 1970. * |
| Instruments",E.W.Golding and F.C.Widdis,pages 686,687(The attracted disc and Kelvin absolute * |
| Oxford University Press 1959. "Electrical Measurements and Measuring * |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9000594D0 (en) | 1990-03-14 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |