GE Multilin C70 Capacitor Bank Protection and Control System 5-2315 SETTINGS 5.7 CONTROL ELEMENTS5The reset time of the thermal overload protection element is also time delayed using following formula:(EQ 5.22)In the above equation,• τrst = thermal protection trip time constant.• Tmin is a minimum reset time settingFigure 5–110: IEC 255-8 SAMPLE OPERATE AND RESET CURVESThe thermal overload protection element estimates accumulated thermal energy E using the following equations calculatedeach power cycle. When current is greater than the pickup level, In > k × IB, element starts increasing the thermal energy:(EQ 5.23)When current is less than the dropout level, I n > 0.97 × k × I B, the element starts decreasing the thermal energy:t rstrstkI B 2I2 kI B 2–----------------------------- ln T min+= ,,SNSW PLQƌUVW ƌRS 7PLQ $&'5E n E n 1–tt op In ---------------+=
