Siemens SG8158-00 manual Demand Setpoints

Protective Function Configuration

2800	50BF Breaker Failure
Address	Parameter	Option
2801	Function	Enabled or Disabled
2802	Pickup	5 A CTs: 0.25-5 A
		1 A CTs: 0.05-1 A
		(0.01 A steps)
2804	Delay	8-254 cycles
2805	Check	current, breaker opened,
		current or breaker opened

The 50BF Breaker Failure function can be enabled and dis- abled (2801). When enabled, the protective function begins monitoring the current flow in the circuit following a trip com- mand by the relay. Simultaneously, the protective function starts a timer. If the current flow does not drop below the pickup value specified (2802) and before the set time delay (2804) has elapsed, a breaker failure is assumed. At this point, another trip command can be issued to a different breaker (via a different output ocntact if available).

The condition of a breaker failure trip depend on the method chosen, the value of the current after the time has run out, and the position of the a and b switches.

The range of the pickup value (2802) is based on the sec- ondary phase CT rating and is in secondary amperes.

The time delay (2804) represents the time between pickup and trip. The delay can be adjusted from 8 to 254 line cycles of delay. The function operates if it remains in pickup for longer than the time delay.

Breaker failure protection monitors the current flow only fol- lowing a trip by the contact identified at address 1004 (see Section 4.2). This is the contact matrixed to the overcurrent protection.

Breaker position is sensed through dedicated binary inputs that monitor the 52a and 52b switches on the breaker mech- anism (breaker mounted). The 52a and 52b switches have a total of four possible position combinations which can be decoded as illustrated in Table 5.3. The 52a and 52b switches referred to are those which traditionally provide indi- cation of circuit breaker position (52b) and trip coil continuity (52a). All error reporting can be enabled and disabled, and the actions to be taken are configurable. Refer to Section 6.6.

Table 5.3 52a and 52b Switches Decoding

52a Switch	52b Switch	Condition Registered
Position	Position
Open	Open	Trip Coil Continuity Error, or
		Breaker Withdrawn
Open	Closed	Circuit Breaker Open
Closed	Open	Breaker Closed
Closed	Closed	Circuit Breaker Mechanism Error

Siemens Energy & Automation, Inc.

Exceptions to the normal operating conditions include the presence of push-to-test switches across either the a-switch, b-switch, or both. A push-to-test switch across the b-switch will produce a false indication of a breaker mecha- nism error when the breaker is actually closed. A push-to test switch across the a-switch (and hence across the trip solenoid) will produce a false indication of a breaker mecha- nism error when the breaker is actually closed.

The Breaker Mechanism function (8305), when enabled, senses an error in the mechanism that controls the position of one or both switches (breaker mechanism error), causes an action to be taken, and an event to be logged if the switches are ever both closed for more than 100 ms. No other time delay is implemented. When this function detects an error, it is considered to be in pickup until the condition is no longer present.

The ISGS relay considers the b-switch to be more reliable. If it senses the switches both open at the same time, the breaker is considered to have a trip coil continuity error or to be withdrawn. The 52a switch closed and the 52b switch open are interpreted as a closed breaker. If the relay senses the 52a switch open and the 52b switch closed, the breaker is considered to be open. Refer also to Table 5.3.

5.18 Demand Setpoints

The ISGS relay is capable of activating outputs and sending events when predefined demand calculations exceed the set thresholds. These setpoints can be enabled or disabled and are capable of activating any output. Measurement and set- point parameters in address block 3100 set the alarm report- ing threshold for the ISGS relay.

The Demand Parameters function selects the time periods for demand calculations performed by the relay and allows the user to enable overcurrent demand and kilowatt demand protection.

3100	Demand Parameters
Address	Parameter	Option
3101	Demand Interval	15, 30, 60 minutes
3102	Sync Time	0, 15, 30, or 45 after hour
3103	Subperiods 60	1, 2, 3, 4, 6, or 12
3104	Subperiods 30	1, 2, 3, or 6
3105	Subperiods 15	1 or 3
3106	I Av Dmd Function	Enabled or Disabled
3107	I Av Dmd Pickup	0-9999 A (1 A steps)
3108	KW Dmd Function	Enabled or Disabled
3109	KW Dmd Pickup	0-999,999 kW (1 kW steps)

Demand intervals (periods) are set to 15, 30, or 60 minutes (3101). Demand calculations are updated at the end of every demand period.

Demand period calculations can begin on the hour or at any quarter hour afterwards. The intervals are indicated as 0, 15, 30, or 45 minutes and are set in the Sync Time parameter (3102).

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