Thytronic DMC3S - Page 62

62
DMC3S - Manual - 08 - 2021
When projection mode detection and two of three - 2/3 trip logic are selected, the start (START) of
any threshold of protection 67 occurs when one of the following two conditions is satisfied:
• the projection of the current phasor for at least one pair of phases along the characteristic axis
I
Lx
cos(θ>-α
x
), I
Lx
cos(θ>>-α
x
), I
Lx
cos(θ>>>-α
x
), I
Lx
cos(θ>-α
x
) (x=1 and 2, 2 and 3, 3 and 1) is positive
and violates the threshold (I
PD>
, I
PD>>
, I
PD>>>
, I
PD>>>>
).
• In at least one pair of phases the fundamental component of the current (I
L1
e I
L2
, I
L2
e I
L3
, I
L3
e I
L1
)
violates the threshold (I
PD>
, I
PD>>
, I
PD>>>
, I
PD>>>>
).
When the threshold starts, so does its timer.
If for the entire operating time of the threshold (t
PD>
, t
PD>>
, t
PD>>>
, t
PD>>>>
) the above condition per-
sists, when the time expires the threshold trips (TRIP), otherwise it resets.
Each threshold of the protection can be enabled or disabled by setting to ON or OFF the parameter
IPD> Enable, IPD>> Enable, , IPD>>> Enable and/orIPD>>>> Enable in the menu
Set \ Protections \ Maximum directional current - 67 \ Threshold IPD> (Threshold IPD>>, Threshold
IPD>>>, Threshold IPD>>>>) \ Parameters.
The first two thresholds can be set to definite or inverse time with the parameter IPD>Curve
and/or IPD>>Curve (IDEFINITE, NIT, VIT, EIT, LIT ) in the menus Set \ Protections \
Maximum directional current - 67 \ Threshold IPD> \ Parameters and Set \ Protections \ maximum
directional current - 67 \ Threshold IPD>>\ Parameters.
The first threshold IPD> can be inhibited when at least one of the three thresholds IPD>>, IPD>>>,
IPD>>>> starts using the Deactivation IPD> by start IPD>>, Deactivation IPD> by start IPD>>>,
Deactivation IPD> by start IPD>>>> (IPD>disbyIPD>>, IPD>disbyIPD>>>, IP-
D>disIPD>>>>) in the menu Set \ Protections \ Overcurrent - 67 \ Threshold IPD>>, Threshold
IPD>>>, Threshold IPD>>>> \ Parameters.
The same applies to the inhibition of:
• Second threshold IPD>> by the start of at least one of IPD>>>, IPD>>>> with the Deactivation IPD>>
by start IPD>>>, Deactivation IPD>> by start IPD>>>> parameters (IPD>>disbyIPD>>>, IP-
D>>disIPD>>>>) in the menu Set \ Protections \ Maximum directional current - 67 \ Thresh-
old IPD>>>, Threshold IPD>>>> \ Parameters.
• Third threshold IPD>>> by the start of the fourth threshold IPD>>>> with the Deactivation IPD>>>
by start IPD>>>> parameter (IPD>>>disIPD>>>>) in the menu Set \ Protections \ Maximum
directional current - 67 \ Threshold IPD>>>> \ Parameters.
Shrink time
For each of the thresholds programmed with definite time characteristic, you can select contracted
time by setting to ON the parameter EnTcIPD>def , EnTcIPD>>def, EnTcIPD>>>def e
EnTcIPD>>>>def and regulating the contracted time (tcIPD>def , tcIPD>>def, tcIP-
D>>>def e tcIPD>>>>def) and operating time (tatcIPD>def, tatcIPD>>def, tatcIP-
D>>>def e tatcIPD>>>>def).
Once the breaker closes, during the operating time (e.g.: tatcIPD>def), the value of the trip time
(e.g.: tPD>def ) is replaced by the contracted time (e.g.: tcIPD>def ); when the operating time
expires the trip time is reset (e.g.: tPD>def ).
The parameters are available in the menu Set \ Protections \ Overcurrent - 67 \ Threshold IPD>
(Threshold IPD>>, Threshold IPD>>>, Threshold IPD>>>>) \ Definite time.
Second harmonic restraint
For each threshold, a second harmonic restraint block can be set by setting to ON the parameter IP-
D>2ndh-REST, IPD>>2ndh-REST, IPD>>>2ndh-REST, IPD>>>>2ndh-REST.
The parameters are available in the menu Set \ Protections \ Overcurrent - 67 \ Threshold IPD>
(Threshold IPD>>, Threshold IPD>>>,Threshold IPD>>>>) \ Parameters.
Functional block (Block3)
If the voltmetric measurement chain fails (function 74VT tripped) or amperometric measurement
chain fails (function 74CT tripped), all thresholds of protection 67 are blocked.