Siemens SIPROTEC 4 User Manual page 218

Functions
2.13 Ground Fault Protection 64, 67N(s), 50N(s), 51N(s)
Direction Determination for cos-ϕ/ sin-ϕ
Addresses 3115 to 3126 are important for direction determination.
Address 3115 67Ns-2 DIRECT determines the direction of the definite high-set current element 50Ns-2 and
can be set to either Forward or Reverse or Non-Directional, i.e. to both directions. The direction of the
current element 50Ns-1 or or 51Ns can be set to Forward or Reverse or Non-Directional, i.e. to both
directions, at address 3122 67Ns-1 DIRECT..
Current value RELEASE DIRECT. (address 3123) is the release threshold for directional determination. It is
based on the current components which are perpendicular to the directional limit lines. The position of the
directional limit lines themselves are based on the settings entered at addresses 3124 and 3125.
The following applies to the determination of direction during ground faults: The pickup current 3Ι0 DIR.
(=RELEASE DIRECT. address 3123) must be set as high as possible to avoid false pickup of the device
provoked by asymmetrical currents in the system and by current transformers (especially in the Holmgreen-
connection).
If direction determination is used in conjunction with one of the current elements discussed above (50Ns-1
PICKUP, addresses 3117 ff, or 51Ns PICKUP, addresses 3119 ff), it is sensible to select a value for address
RELEASE DIRECT. that is lower than or equal to the above pickup value.
A corresponding message (reverse, forward, or undefined) is issued upon direction determination. To avoid
chatter for this message resulting from extremely varying ground connection currents, a dropout delay RESET
DELAY, entered at address 3126, is initiated when directional determination drops out, and the message is
held for this period of time.
When address 3124 PHI CORRECTION is set to 0.0°, in address 3125 the following signifies
•
MEAS. METHOD = COS φ
the resistive component of the ground current with respect to the displacement voltage is most relevant
for the current value RELEASE DIRECT. (3Ι0 DIR.),
MEAS. METHOD = SIN φ
the reactive (capacitive) component of the ground current with respect to the displacement voltage is
most relevant for the current value RELEASE DIRECT. (3Ι0 DIR.)
218
(Figure 2-97).
SIPROTEC 4, 7SJ62/64, Manual
C53000-G1140-C207-8, Edition 08.2016