Claims
- 1. A protection device for low-voltage networks, comprising:a measurement device, including a current transformer, for determining instantaneous values of a current and a current rate of change and an evaluation device which acts as a unit for early short-circuit identification, and which uses the instantaneous values of the current and the current rate of change to identify a short-circuit, wherein the current transformer is a multiwinding transformer based on a printed circuit board including at least two secondary windings with signals for the current and for the current rate of change being determined from the at least two secondary windings.
- 2. The protection device as claimed in claim 1, wherein the evaluation device includes a first unit which operates on the basis of determining predetermined values of the signals for the current and current rate of change.
- 3. The protection device as claimed in claim 2, wherein the product of the current and the current rate of change is taken into account as a limit value in the evaluation device.
- 4. The protection device as claimed in claim 3, wherein the product (i·di/dt) of the current (i) and the current rate of change (di/dt) is given by the relationship: ⅆiⅆt·i>GProduct≈ω·IN2·2·[1+1,6·exp (-17·cos φN)]⇒short circuit,whereGproduct: Tripping threshold value, wherein a short circuit is present if this value is exceeded) IN: Root mean square value of the rated current ω: Circular frequency of the network COSφN: Power factor of the network during rated operation.
- 5. The protection device as claimed in claim 2, wherein the evaluation device includes a second unit which operates on the basis of tolerance locus curves (TLC method), with locus curves which take account of different power factors (0.1<cos φ<0.9) being used as tripping criteria in a locus curve representation of the current and current rate of change.
- 6. The protection device as claimed in claim 5, wherein the second unit, which operates using the TLC method, includes digital switching means.
- 7. The protection device as claimed in claim 5, wherein analog/digital converters are connected between the multiwinding transformer and the evaluation device.
- 8. The protection device as claimed in claim 7, wherein the unit, which operates using the TLC method, includes analog switching means.
- 9. The protection device as claimed in claim 6, wherein analog/digital converters are connected between the multiwinding transformer and the evaluation device.
- 10. The protection device as claimed in claim 9, wherein the second unit, which operates using the TLC method, includes analog switching means.
Priority Claims (1)
Number |
Date |
Country |
Kind |
198 39 616 |
Aug 1998 |
DE |
|
Parent Case Info
This application is the national phase under 35 U.S.C. § 371 of PCT International Application No. PCT/DE99/02594 which has an International filing date of Aug. 18, 1999, which designated the United States of America.
PCT Information
Filing Document |
Filing Date |
Country |
Kind |
PCT/DE99/02594 |
|
WO |
00 |
Publishing Document |
Publishing Date |
Country |
Kind |
WO00/13281 |
3/9/2000 |
WO |
A |
US Referenced Citations (7)
Foreign Referenced Citations (2)
Number |
Date |
Country |
C1-19729599 |
Feb 1999 |
DE |
A2838887 |
Apr 1998 |
EP |