Siemens SG8158-00 manual Directional Neutral or Ground Time Overcurrent 67N

Protective Function Configuration

The Directional Phase Time Overcurrent function can be enabled or disabled (1901).

The Curve parameter (1902) allows the selection of the pre- programmed characteristic curve used by this function. The ISGS relay comes with nine standard overcurrent character- istic curves that can be adjusted with the Time Dial parame- ter. The custom curve is a user-definable protective curve that integrates with instantaneous reset. The lower limit of the custom curve is 1.10. The maximum time to trip is the time at 1.10.

The range of the pickup value (1903) depends on the sec- ondary phase CT rating (1 A or 5 A) and the value is in sec- ondary amperes. The function begins timing when any individual phase current exceeds the pickup current setting.

The Time Dial parameter (1905) used for the selected curve allows the time-to-trip of the curve to be raised or lowered The dial can be adjusted from 0.1 to 9.9 in steps of 0.1.

The Filter parameter (1906) sets the sensing method used by the function in its pickup calculations. The rms filter uses fun- damental current plus harmonics, while the fundamental filter ignores harmonics.

Impedance (1907) sets the angle used by this function. Impedance determines the direction of current flow being measured and can be set from 0 to 90 degrees. The direc- tional characteristic (line) in the complex impedance plane is shown in Figure 5.2. The directional characteristic is always perpendicular to the line impedance vector.

The sensing direction (1908) can be set to forward or reverse. The forward setting allows the directional protection element to pickup on fault current only in the direction oppo- site to normal power flow.

Each of the two waveform capture buffers (1910 and 1911) can be independently programmed to freeze snapshots on pickup or trip.

The function is able to actuate any binary output contact on pickup, and any trip or binary output contact on trip.

5.10Directional Neutral or Ground Time Overcurrent (67N)

The Directional Neutral or Ground Time Overcurrent function uses a selected time overcurrent characteristic curve to determine the trip time for the applied current at the fourth current input, utilizing the voltages present on the VTs to determine current direction. The defined characteristic curves are valid over a range of multiple of pickup values. The function also includes a customer defined curve. Refer to Appendix A for detailed trip curve information. This func- tion is only available if the voltage input option is installed.

A2000	Directional Neutral or Ground Time Overcurrent
	(67N)
Address	Parameter	Option
2001	Function	Enabled or Disabled
2002	Curve	Inverse
		Short Inverse
		Long Inverse
		Moderately Inverse
		Custom
		Very Inverse
		Extremely Inverse
		Definite Inverse
		Slightly Inverse
		I2T Without Limit
2003	Pickup	5 A CTs: 0.5-20 A or
		1 A CTs: 0.1-4 A
		(0.1 A steps)
2005	Time Dial	0.1-9.9 (0.1 steps)
2006	Filter	rms or fundamental
2007	Impedance	0-90°
2008	Direction	Forward or Reverse
2010	Freeze Wfm1	on Pickup, on Trip, or None
2011	Freeze Wfm2	on Pickup, on Trip, or None

The Directional Neutral or Ground Time Overcurrent function can be enabled or disabled (2001).

The Curve parameter (2002) allows the selection of the pre- programmed characteristic curve used by this function. The ISGS relay comes with nine standard overcurrent character- istic curves that can be adjusted with the time dial parameter (see below). The custom curve is a user-definable protective curve that integrates with instantaneous reset. The lower limit of the custom curve is 1.10. The maximum time to trip is the time at 1.10.

5

Figure 5.2 Directional Characteristic

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