Page 57 - MCCB-XT5

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Parameter Description Default
This is the voltage that determines the change in trip threshold
I20; the behavior differs, depending on the mode selected (1)
Threshold Ul The value is given as both absolute value (V) and relative value 1 Un
(Un) and can be set within the range: 0.2 Un to 1 Un in 0.01 Un
steps
The parameter is shown by the Lin curve and contributes towards
I20 trip threshold calculation:
• with voltage reading < Uh (and ≥ Ul), the threshold changes
gradually (1)
Threshold Uh 1 Un
• with voltage reading ≥ Uh, the threshold is I20
The value is given as both absolute value (V) and relative value
(Un) and can be set within the range: 0.2 Un to 1 Un in 0.01 Un
steps
I20 threshold calculation constant.
Threshold Ks The value is given as percentage of threshold I20 and can be set 0,6 I20
within the range: 0.1 I20 to 1 I20, in 0.01 steps
This is the trip time of the protection.
Time t20 The value is given in seconds and can be set within the range: 0.1 s
0.05 s to 30 s, in 0.01 s steps

(1) Trip threshold (depending on the operating curve)
Mode Voltage reading Trip threshold
< UI Ks x I20
Scal
≥ UI I20
< UI Ks x I20
Lin
≥ Ul (e < Uh) ((I20 x ( 1 - Ks ) x ( U - Uh ) ) / (Uh - Ul) ) + I20
mis
Limitations and additional functions
The block functions can also be accessed by means of the service connector (via Ekip Connect) or by
connection to the system bus (page 76).

S(V) Protection Function
S2(V) protection functions in the same way as S(V) protection and protects against short-circuits, with
t threshold sensitive to the voltage value.
I21 S2(V) It is independent of S(V) protection, thus thresholds and functions of the two protections can be
programmed so as to take advantage of different plant solutions (example: signaling with S(V) and open
command with S2(V) or vice versa, or both S(V) and S2(V) for signaling or tripping).
t21
If the current of one or more phases exceeds threshold I21 for longer than time t21, the protection activates
and sends a TRIP command.
I
Following a voltage drop, the I21 threshold varies according to two different modes:
• Step provides for a stepped variation, depending on parameters Ul2 and Ks2.
• Lin (linear) provides for a dynamic variation, depending on parameters Ul2, Uh2 and Ks2.
I21 I21

I21 I21

Ks2 x I21 Ks2 x I21

Ul2 V Ul2 Uh2 V

Figure 28
To check and simulate the trip times in relation to all the parameters, please consult:
• the summary table of the protections with the calculation formulas (page 82)
• the graph with trip curve (page 93)

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55 | © 2022 ABB | 1SDH002039A1002 - ECN000212994 Protections | 4 - Voltage Advanced protections