Figure 181: TCS Scheme 3
When the CB is closed, supervision current passes through the opto-input, resistor R2 and the trip coil. When the
CB is open, current flows through the opto-input, resistors R1 and R2 (in parallel), resistor R3 and the trip coil. The
supervision current is maintained through the trip path with the breaker in either state, therefore providing pre-
Resistors R1 and R2 are used to prevent false tripping, if the opto-input is accidentally shorted. However, unlike the
other two schemes. This scheme is dependent upon the position and value of these resistors. Removing them
would result in incomplete trip circuit monitoring. The table below shows the resistor values and voltage settings
required for satisfactory operation.
Trip Circuit Voltage
This Scheme is not compatible with Trip Circuit voltages of less than 48 V.
PSL FOR TCS SCHEME 3
*NC stands for Normally Closed.
Figure 182: PSL for TCS Scheme 3
Opto Voltage Setting with R1
Resistor R1 & R2 (ohms)
Chapter 15 - Supervision
Resistor R3 (ohms)