System information

GRAVITAS SABRE SERIES
INSTALLATION &OPERATING MANUAL
Manual No. SABRE-4 Page 21 11/27/07 sabre-man
1.2.1.11 Overload/output short circuit protection
1.2.1.11.1 Overload protection
<1> Method one
When the STS is operating in either On-line or Off-line mode, the load current will be calculated in the firmware
automatically. This calculation will be used in the overload protection function. With 20S time of 120% overload, or
5S time of 160% overload, the system will cease to provide output power, and the static switch will send an “Overload”
alarm to the controller. (Note: The STS will need to have all power recycled to restart from this condition).
<2> Method two
The STS will estimate the load capability of the system based on the number of installed inverters reported by the
controller. For the INV1048 the definition of rated power in VA is “inverter number x 1000VA”, with rated active
power “VA x 0.8”. For the INV1548 the definition of rated power in VA is “inverter number x 1500VA”, with rated
active power “VA x 0.8”. When the Utility has priority the STS operates in off-line mode. With a change of priority
to the Inverter the STS will estimate the load capability of the Inverters to decide whether to transfer to on-line mode.
If the current load exceeds the load capability of the Inverters the STS won’t transfer to on-line mode, otherwise it will
transfer to on-line mode approximately 6 seconds later.
As an exception, the STS will immediately transfer to on-line mode without estimating the load capability of the
Inverters when the utility voltage or frequency is abnormal.
1.2.1.11.2 Output short protection
Based on the different priorities, output short protection has different methods to deal with each situation.
<1> Mains priority
If the Inverter is operating normally when the output short happens the STS will transfer to Inverter mode, then
“Output short protection” will be sent to controller and finally the STS will transfer to fault mode
If the Inverter is faulty or off when the output short happens the STS will shut off the output and an “Output short
protection” message will be sent to controller (if present).
<2> Inverter priority
If the Mains is normal when the output short happens the STS will transfer to Mains mode, and then an “Output
short protection” message will be sent to the controller.
If the Mains is abnormal or not present when the output short happens the STS will send an “Output short
protection” message and then transfer fault mode.
Note᧶Damage to the STS will occur if the short current exceeds 2400A.