Utilidad y funcionalidad

A. The System Controls shall include a Load Shed Control function to control the loads served by the generator plant. The Load Shed Control shall have one Essential Load Shed Priority Level for each generator in the system plus one Non-Essential Load Shed Priority Level (which is always shed in the Emergency Mode of operation). The Load Shed Control shall provide a 4 pole, 10A, 120VAC rated, form C set of contacts for each Load Shed Priority Level to allow the

control of loads external to the Emergency Generator Paralleling Switchboard.

Additionally, the Load Shed Control shall control each of the distribution circuit breakers within the Emergency Generator Paralleling Switchboard, which are shown on the drawings to be electrically operated. Each electrically operated distribution circuit breaker shall be field selectable to be assigned to any of the available Load Shed Priority Levels. The following controls shall be provided for each Essential Load Shed Priority:

1) One - Shed Delay Timer, adjustable from 0 to 255 minutes 2) One - Add Delay Timer, adjustable from 0 to 255 minutes

3) One - Load Shed By-Pass Selector (auto/manual shed/manual add)

4) Three - Status indicators to show the 3 positions of the Load Shed By-Pass Selector

5) Two - Status indicators to show whether the Priority Level is Added or Shed

B. The following controls shall be provided for the Non-Essential Load Shed Priority:

1) One - Load Shed By-Pass Selector (auto/manual shed/manual add) 2) Three-Status indicators to show the 3 positions of the Load Shed By-Pass Selector

3) Two-Status indicators to show whether the Priority Level is Added or Shed C. Additionally, the Load Shed Controls shall have:

1) One - Load Shed Control Switch (On/Off)

2) One - User-settable Load Shed % (as a function of on-line generator capacity) 3) One - User-settable Load Add % (as a function of on-line generator capacity) 4) One - User-settable Bus Underfrequency Setpoint and time delay

5) One - Bus Frequency Normal indicator 6) One - Bus Underfrequency indicator D. Conditional/Load Sensitive

1) Conditional Load Shed: Upon entrance into Emergency Mode of operation, the Load Shed Control shall shed all Non-Essential loads. As generators come to the bus, Non-Essential Priority Level loads shall be added based on the number of generators on line. When the first generator comes to the bus, Priority Level 1 loads shall be added; second generator, priority 2, etc. After a time delay that allows all operational generators to come to the bus, Load Shed Mode shall shift to Load Sensitive Mode. (Provided the Load Shed Switch is in ON)

2) Load Sensitive Load Shed: After all generators have been given sufficient time to come to the bus, load shed shall shift to “Load Sensitive” mode. The system shall compare current generator on-line capacity (in kW) to current load

requirements. If surplus capacity is greater than the calculated Load Add Setpoint, after the Load Add Time Delay the next Load Shed Priority will be added. This calculation will continue until all Sheddable Loads are added, or until surplus capacity is less than the calculated Load Add Setpoint. If surplus capacity is less than the calculated Load Shed Setpoint, after the Load Shed Time Delay the next Load Shed Priority will be shed. This calculation will continue until all Sheddable Loads are shed, or until surplus capacity is greater that the calculated Load Shed Setpoint. The Load Shed Control, in its automatic shedding and adding of loads, shall not override any manual load shed/add operation.

E. Should a generator fail off-line or should loads increase, Essential Priority Level loads shall be shed as a function of the on-line generator capacity by the user selected load shed time delays and within the user selected load shed limits. The Load Shed Control, in it's automatic shedding of loads, shall not override any manual load add operation.

F. Should the load bus frequency fall below the user selected bus

underfrequency, then an alarm is triggered and displayed on the system alarm summary.

Under Frequency Setpoint Under Frequency Alarm Indicator

 Load Shed Under frequency Trip (Located on Load Shed Control Screen): 55Hz

 Load Shed Under frequency Alarm (Located on the System Annuncation Screen) (a) How to set Load Shed Bus Under frequency and associated Alarm

 From Overview Screen

 Press the CONTROL button: Pop up boxes will show.

 Press the SYSTEM button: this will take you to “System Control Screen”

 Press the LOAD SHED CONTROL button: this will take you to “Load Shed Control Screen”

OR

 From Overview Screen

 Press the MAIN MENU button: this will take you to the “Main Menu Screen”.

 Press the SYSTEM CONTROL button: this will take you to “System Control Screen”

 Press the LOAD SHED CONTROL button: this will take you to “Load Shed Control Screen”

(b) Required Switch Positions

Load Sense Switch Load Shed Level Switch Distribution Control Switch

 Load Sense Switch (Located on Load Shed Control Screen): On

 Load Shed Level Switches (Located on Load Shed Control Screen): Auto

 Distribution Control Switches (Located on Load Shed Control Screen): Auto

(c) How to set Load Shed Levels Hardwire

 The Load Shed Control shall provide a 4 pole, 10A, 120VAC rated, form C set of contacts for each Load Shed Priority Level

 Each Priority can be manually added or shed from the Touch Screen Electrically operated breakers

 Each electrically operated distribution circuit breaker shall be field selectable to be assigned to any of the available Load Shed Priority Levels