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NC2 0 - Manual - 01 - 2015

FUNCTION CHARACTERISTICS

Undercurrent - 37

Preface

Two operation thresholds, independently adjustable with adjustable delay and deﬁ nite time charac-

teristic.

The ﬁ rst one operates with OR logic, while the second threshold operates with AND logic.

Both thresholds may be temporarily disabled by MMI command.

Each threshold may be separately enabled or disabled.

Operation and settings

The RMS phase currents I

L1RMS

, I

L2RMS

, I

L3RMS

(including up to eleventh harmonic) are compared

with the setting values (I<

def

, I<<

def

For the ﬁ rst threshold a start is issued when at least one of the three currents goes down the adjust-

able threshold (OR logic), while, for the second threshold, a start is issued when all the three currents

go down the adjustable threshold (AND logic).

After expiry of the associated operate time (t<

def

, t<<

def

) a trip command is issued; if instead the cur-

rents exceed the threshold, the element is restored.

Each element can be enabled or disabled by setting ON or OFF the State parameter inside the Set

\ Proﬁ le A(or B) \ Undercurrent-37 \ I< (I<< Element) \ Deﬁ nite time

All the named parameters can be set separately for Proﬁ le A and Proﬁ le B (Set \ Proﬁ le A(or B) \

Undercurrent - 37 \ I< Element (I<< Element) \ Setpoints menus).

For every of the two thresholds the logic block can be set.

Logical block (Block1)

If the I<BLK1 and/or I<<BLK1 enabling parameters are set to ON and a binary input is designed

for logical block (Block1), the protection is blocked off whenever the given input is active.

The trip timer is held in reset condition, so the operate time counting starts when the input block

goes down.

[1]

The enabling parameters are available inside the Set \ Proﬁ le A(or B) \ Undercurrent

- 37 \ I< Element (I<< Element) \ Setpoints menus, while the Block1 function must be assigned to the

selected binary input inside the Set \ Inputs \ Binary input IN1(x) menus (IN1 or INx matching).

Note 1 The exhaustive treatment of the logical block (Block 1) function may be found in the “Logic Block” paragraph inside CONTROL AND MONITOR-

ING section.

t-int-F37.ai

RMS

I<< I<

t<<

General operation time characteristic curve for the undercurrent elements - 37

TRIP

t-int-F37.ai

RMS

I<< I<

t<<

General operation time characteristic curve for the undercurrent elements - 37

TRIP

all-F37.ai

L1RMS

, I

L2RMS

, I

L3RMS

L1RMS

, I

L2RMS

, I

L3RMS

MMI

I<< Element I< Element

Disable 37 elements

Start I<< Start U<

Trip U<Trip I<<

I< inhibition I<< inhibition

def

I<<

def

State State

Block1

BLK1I<

I<BLK1

Start I<

Block1

BLK1I<<

I<<BLK1

Start I<<

General logic diagram of the undercurrent elements - 37

all-F37.ai

L1RMS

, I

L2RMS

, I

L3RMS

L1RMS

, I

L2RMS

, I

L3RMS

MMI

I<< Element I< Element

Disable 37 elements

Start I<< Start U<

Trip U<Trip I<<

I< inhibition I<< inhibition

def

I<<

def

State State

Block1

BLK1I<

I<BLK1

Start I<

Block1

BLK1I<<

I<<BLK1

Start I<<

General logic diagram of the undercurrent elements - 37

Brand	Thytronic
Model	NC20
Category	Power distribution unit
Language	English

Thytronic NC20 User Manual

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