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Multi-input distance relayMulti-input distance relay
By: Nikhil Kushwaha10M212
OutlineOutlineIntroductionPrincipleConic section charactersticsQuadrilateral charactersticsSweivelling charactersticsConclusionRefrences
IntroductionIntroductionWhen the inputs are raised to more
than two, then they are termed as multi-input comparators and they could be either amplitude or phase comparator or a combination of two.
With multiple-inputs duality between the comparators no longer exists.
They give non-classical characterstics.
PrinciplePrincipleIn recent years, greater attention has
been paid to distance relaying techniques of transmission lines. The main target of these techniques is to calculate the impedance the fundamental frequency between the relay and fault point. According to the calculated impedance, the fault is identified as internal or external to the protection zone. This impedance is calculated from the measured voltage and current signals at the relay location.
Conic section Conic section charactersticscharactersticsEllipseParabolaHyperbolaLimacon
Elliptical CharactersticsElliptical Characterstics
Parabolic characterstics :Such a characterstic can be used as blinder, i.e. To limit the area of another relay on R-X diagram
Hyperbolic characterstics :Can be realized using multi-input comparator. For the operation following condition should be satisfied:|Z-Zr|-|Z-KZr| < |Zr+KZr|
LimaconCharacterstics :They are use as blinders.ILZR [Kcos(ϕ-θ)-1]= VL
Multilateral or Multilateral or QuadrilateralQuadrilateral
Theoritically the ideal characterstics for distance relays would be a quadrilateral characterstics coincident with fault area.
Realisation of Quadrilateral Characterstics
Various characterstics resulting from the phase comparison of inputs indicated in the previous figure
θ
INTERPHASE SWITCHINGINTERPHASE SWITCHING
SWIVELLING SWIVELLING CHARACTERSTICSCHARACTERSTICSReactance relay is suitable for short lines.MHO relay is for long Tx lines. It will be better if a relay changes its
characteristics when line impedance ZL changes.
A circular relay characteristic is desirable for low ZS/ZL & straight line characteristic for high ZS/ZL.
To realize such characteristics, a fully cross-polarized MHO relay is used.
Such a relay operates reliably when a close-up fault occurs.
ZS/ZL = ∞
ZS/ZL = 0
ZS/ZL = 1
SWIVELLING CHARACTERSTICS
CONCLUSIONCONCLUSIONApplication of multiple input
comparators till now has been found in the field of distance relays.
Relays control output circuits of a much higher power.
Safety is increasedProtective relays are essential for
keeping faults in the system isolated and keep equipment from being damaged.
REFRENCESREFRENCES1. Power System Protection Static Relays : T S MADHAVA RAO.
2. Power System Protection and Switchgear : BADRI RAM & D N VISHWAKARMA.
3. Shrivastava, Kiran and Vishwakarma, D. N.(2007) 'Microcontroller-Based Numerical Quadrilateral Relay for the Transmission Line Protection', Electric Power Components and Systems.
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