sepam series 80 neutral voltage displacement

8/17/2019 Sepam Series 80 Neutral Voltage Displacement

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Metering functions Residual voltageNeutral point voltage

Residual voltage

OperationThis function gives the following values:

b main residual voltage

b additional residual voltage

The residual voltage value may be:

b calculated by an open star/delta VT

b or calculated by taking the internal sum of the 3 phase voltages.

It is based on the measurement of the fundamental 50 Hz or 60 Hz component

of the voltages.

ReadoutThe measurements may be accessed via:

b the Sepam display via the key

b the display of a PC with the SFT2841 softwareb the communication link.

CharacteristicsMeasurement range 0.015 to 3 Vnp (1)

Units V or kV

Resolution 1 V

Accuracy ±1 % from 0.5 to 3 Vnp±2 % from 0.05 to 0.5 Vnp±5 % from 0.02 to 0.05 Vnp

Display format 3 significant digits

Refresh interval 1 second (typical)

(1) Vnp: primary rated phase-to-neutral voltage (Vnp = Unp/ 3 ).

Neutral point voltageOperationThis function gives the value of the zero sequence voltage Vnt, measured at theneutral point of a generator or motor by a dedicated VT:

ReadoutThe measurements may be accessed via:

b the Sepam display via the keyb the display of a PC with the SFT2841 software

b the communication link.

CharacteristicsMeasurement range 0.015 Vnp to 3 Vntp (1)

Units V or kV

Resolution 1 V

Accuracy ±1 % from 0.5 to 3 Vntp±2 % from 0.05 to 0.5 Vntp±5 % from 0.02 to 0.05 Vntp

Display format 3 significant digits

Refresh interval 1 second (typical)

(1) Vntp: neutral point voltage transformer primary voltage.

V0 V1 V2 V3+ +=

′ 0 V′ 1 V ′ 2 V′+ +=

nt V1 V2 V3+ +( ) 3 ⁄ =


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Protection functions Neutral voltage displacementANSI code 59N

Protection against insulation faults DescriptionProtection against insulation faults by measuring the residual voltage V0 or the

neutral point voltage Vnt for generators and motors.

The residual voltage is obtained by the vector sum of the phase voltages or bymeasurements using delta connected VTs.

The neutral point voltage is measured by a VT inserted in the neutral point of the

generator or the motor.

The protection function includes a time delay T, either definite or IDMT (dependenton the residual voltage V0) (see tripping curve equation on page 226).

It operates only when a residual or neutral point voltage is available, by connecting

V1V2V3, V0 or Vnt.

Block diagram

D E 5 0 7 8 5

CharacteristicsSettings

Measurement origin

Setting range Main channels (V0)Additional channels (V’0)Neutral-point voltage (Vnt)

Tripping curve

Setting range Definite timeIDMT (dependent on the residual voltage V0)

Vs0 set point

Definite time setting range 2 % Unp to 80 % Unp (for residual voltage V0)2 % Vntp to 80 % Vntp (for neutral point voltage Vnt)

IDMT setting range 2 % Unp to 10 % Unp (for residual voltage V0)2 % Vntp to 10 % Vntp (for neutral point voltage Vnt)

Accuracy (1) ±2 % or 0.005 Unp

Resolution 1 %

Drop out/pick up ratio 97 % ±2 % or > (1 - 0.006 Unp/Vs0) x 100 %

Time delay T (tripping time at 2 Vs0)

Definite time setting range 50 ms to 300 s

IDMT setting range 100 ms to 10 s

Accuracy (1) ±5 % or ±25 ms

Resolution 10 ms or 1 digit

Characteristic times

Operation time pick-up < 45 ms (typically 25 ms) at 2 Vs0

Overshoot time < 40 ms at 2 Vs0

Reset time < 40 ms at 2 Vs0

Inputs

Designation Syntax Equations Logipam

Protection reset P59N_x_101 b b

Protection inhibition P59N_x_113 b b

Outputs

Designation Syntax Equations Logipam Matrix

Instantaneous output (pick-up) P59N_x_1 b b

Delayed output P59N_x_3 b b b

Protection inhibited P59N_x_16 b b

x: unit number.(1) Under reference conditions (IEC 60255-6).


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Protection functions GeneralTripping curves

Current IDMT tripping curvesMultiple IDMT tripping curves are offered, to cover most applications:

b IEC curves (SIT, VIT/LTI, EIT)

b IEEE curves (MI, VI, EI)b commonly used curves (UIT, RI, IAC).

IEC curves

Equation Curve type Coefficient values

k α βStandard inverse / A 0.14 0.02 2.97

Very inverse / B 13.5 1 1.50

Long time inverse / B 120 1 13.33

Extremely inverse / C 80 2 0.808

Ultra inverse 315.2 2.5 1

RI curve

Equation:

IEEE curves


A B p βModerately inverse 0.010 0.023 0.02 0.241

Very inverse 3.922 0.098 2 0.138

Extremely inverse 5.64 0.0243 2 0.081

IAC curves


A B C D E βInverse 0.208 0.863 0.800 -0.418 0.195 0.297

Very inverse 0.090 0.795 0.100 -1.288 7.958 0.165

Extremely inverse 0.004 0.638 0.620 1.787 0.246 0.092

Voltage IDMT tripping curvesEquation for ANSI 27 - Undervoltage Equation for ANSI 59N - Neutral voltage displacement

Voltage/frequency ratio IDMT tripping curvesEquation for ANSI 24 - Overfluxing (V/Hz) Curve type p

Where G = V/f or U/f A 0.5

B 1

C 2

td I( )k

I

Is----

α 1–

--------------------T

β---×=

td I( )1

0.339 0.236I

Is----

1––

-----------------------------------------------------T

3.1706------------------×=

d I( )A

I

Is----

p 1–---------------------- B+

T

β---×=

td I( ) AB

I

Is---- C–

-------------------

D

I

Is---- C–

2----------------------

E

I

Is---- C–

3----------------------+ + +

xT

β-----=

td V( ) T1

V

Vs------

–

---------------------=td V( )

T

V

Vs-------

1–----------------------=

td

G( )1

G

Gs------- 1–

p------------------------- x T=

sepam series 80 neutral voltage displacement

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