Fast distance protection for energy supply networks

Patent metadata

Field	Value
Publication number	US-9478968-B2
Application number	US-201013809086-A
Country	US
Kind code	B2
Filing date	Jul 9, 2010
Priority date	Jul 9, 2010
Publication date	Oct 25, 2016
Grant date	Oct 25, 2016

Abstract

A method for detecting a short circuit on a multiphase electrical energy supply network line includes recording current and voltage sampled values and generating a fault signal upon a fault evaluation performed by an electrical protection device indicating a short circuit. Instantaneous reference voltage values are calculated from instantaneous current and voltage sampled values recorded before the short, and instantaneous comparative voltage values are calculated from instantaneous current and voltage sampled values recorded before the short and instantaneous current and voltage sampled values recorded during the short, to generate a fault signal quickly. Then a rectified reference voltage value is calculated from consecutive instantaneous reference voltage values, and a rectified comparative voltage value is calculated from consecutive instantaneous comparative voltage values. The fault signal is generated if a difference between rectified comparative voltage and rectified reference voltage values exceeds a triggering threshold value. A corresponding electrical protection device is provided.

First claim

The invention claimed is:

1. A method for detecting a short circuit on a line of a multi-phase electrical energy supply network with grounded neutral, the method comprising the following steps: recording current and voltage sampled values at a measurement point at one end of the monitored line by an electrical protection device; generating a first fault signal indicating a short circuit on the line if a fault evaluation of the current and voltage sampled values performed by the electrical protection device indicates a short circuit present on the line; and performing the following steps for fault evaluation of the current and voltage sampled values: calculating instantaneous reference voltage values for a reference point on the line from instantaneous current and voltage sampled values recorded before an occurrence of the short circuit; calculating instantaneous comparative voltage values for the reference point on the line from instantaneous current and voltage sampled values recorded before the occurrence of the short circuit and instantaneous current and voltage sampled values recorded during the short circuit; calculating a rectified reference voltage value from consecutive instantaneous reference voltage values and a rectified comparative voltage value from consecutive instantaneous comparative voltage values; comparing the rectified reference voltage value and the rectified comparative voltage value; generating the first fault signal if a difference between the equivalent comparative voltage value and the rectified reference voltage value exceeds a triggering threshold value; and calculating the rectified reference voltage value by the following equation: U ref (n)=2 Nk=n−(N2−1)n(u ref (k)) ##EQU00011## where U.sub.ref(n): rectified reference voltage value; u.sub.ref(k): instantaneous reference voltage value for the sampled value k; n: number of the sampled value after fault occurrence; N: number of sampled values per period; k: summation index; and calculating a rectified comparative voltage value in accordance with the following equation: UV(n)=2Nk=n−(N2−1) n(uV(k)) ##EQU00012## where U.sub.v(n): rectified comparative voltage value; u.sub.v(k): instantaneous comparative voltage value for the sampled value k; n: number of the sampled value after fault occurrence; N: number of sampled values per period; and k: summation index.

2. The method according to claim 1 , which further comprises calculating the instantaneous reference voltage values by the following equation:

u
ref

⁡

(
n
)

=

u
p

⁡

(
n
)

-

L
ref

⁢

i
p

⁡

(
n
)

-

i
p

⁡

(

n
-
1

)

T

-

R
ref

·

i
p

⁡

(
n
)

,

where
u ref (n): instantaneous reference voltage value;
u p (n)=u(n−N): pre-fault voltage sampled value a period before the instantaneous voltage sampled value u(n);
i p (n)=i(n−N): pre-fault current sampled value a period before the instantaneous current sampled value i(n);
T: period;
N: number of sampled values per period;
n: number of the sampled value after fault occurrence;
L ref : inductance of the line from the measurement point to the reference point; and
R ref : resistance of the line from the measurement point to the reference point.

3. The method according to claim 1 , which further comprises calculating the instantaneous comparative voltage values by the following equation:

u
v

⁡

(
n
)

=

Δ
⁢

⁢

u
f

⁡

(
n
)

-

L
ref

⁢

Δ
⁢

⁢

i
f

⁡

(
n
)

-

Δ
⁢

⁢

i
f

⁡

(

n

Assignees

• Blumschein Joerg
• Dzienis Cezary
• Kereit Matthias
• Siemens Ag

Inventors

• Blumschein Joerg
• Dzienis Cezary
• Kereit Matthias

Classifications

• G01R31/085

  in power transmission or distribution lines, e.g. overhead · CPC title

• H02H7/26

  Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured (locating faults in cables G01R31/08) · CPC title

• H02H1/0092 Primary

  concerning the data processing means, e.g. expert systems, neural networks · CPC title

• G01R31/025

  Physics · mapped topic

• G01R31/52 Primary

  Testing for short-circuits, leakage current or ground faults · CPC title