ABB Distribution Protection Unit 1500R
1-23
Protective Functions
9/99
website:www.abb.com/papd
Cold Load Time
The Cold Load timer as set in the Primary, Alternate 1, and Alternate 2 settings groups is used to block unintentional
tripping of the 50P-1 and the 50N-1 due to inrush currents seen by the DPU1500R after a manual breaker close. The
timer is set from 0 to 254 with a resolution of 1. Select “seconds” or “minutes” in the Configuration Settings (see Section
2). During the cold load time delay period, a logical output, CLTA, is asserted. This logical output can be mapped to a
physical output for alarm and control purposes (see Programmable Outputs Section). The cold load timer is operational
only after a manual breaker close. It does not operate during a DPU1500R reclose sequence.
The Cold Load Time is disabled in the factory default settings.
A separate Neutral Cold Load Time function is supplied in units with the Sensitive Earth Fault feature.
Recloser Function 79 (O->I)
This recloser function, 79, provides automatic reclosing of the circuit breaker after the DPU1500R has tripped due to
a fault. The circuit breaker will close after a preprogrammed time delay called “Open Time”. Zero to four recloser steps
can be selected and each has its own separate “Open Time” and selection of protective elements. The steps as labeled
in the DPU1500R are 79-1 (step 1), 79-2 (step 2), 79-3, (step 3), 79-4 (step 4) and 79-5 (step 5). During each reclose
step the protective elements 50P-1, 50P-2, 50P-3, 51N, 50N-1, 50N-2, and 50N-3 can be enabled or disabled from
tripping. Each protective element can also be set such that if the element operates, the reclose sequence will be
halted and “locked out”. Lockout is a point at which the circuit breaker will remain open after a fault and must be
manually closed. These steps can be used to provide high speed reclosing for the first trip and delayed reclosing
thereafter. A reset timer runs after a successful circuit breaker reclose (whether automatic or manual) and is used to
reset the reclose sequence to 79-1 after its time period expires. If the DPU1500R trips the circuit breaker again before
the expiration of the reset time, the reclose sequence will increment one step; I.E. 79-1 to 79-2. The settings as
programmed in the 79-2 step will then become active. This incremental stepping occurs until the recloser locks out or
successfully recloses. If the reclosing function proceeds to lockout, the circuit breaker must be manually closed.
Undervoltage Element 27 (U<)
The undervoltage element is provided for
alarm and control purposes when the
system voltage drops below a preset
threshold. Two logical outputs are provided
with the 27 element; one for single phase
undervoltage, 27-1P, and one for three phase
undervoltage, 27-3P. The 27-1P element will
operate when any single phase drops below
the undervoltage setting. The 27-3P element
will operate only when all three phases drop
below the undervoltage setting. Both
elements are separate and do not operate the “Main Trip” contact. These logical outputs must be mapped to physical
outputs if alarming or tripping is desired (see Programmable I/O Section). The 27 element can also be used to
supervise (torque control) other protective elements such as the 51P. Mapping the 27 element to the “PH3” logical input
via the programmable logic, provides a voltage controlled overcurrent protective function. See the “Programmable I/O”
Section for more details.
The 27 threshold and time delay are set in the Primary, Alternate 1, and Alternate 2 settings groups (Table 5-1). The
time delay range is 0 to 60 seconds. If trip times below one second are desired, set the Time Delay to zero and place
desired trip time in physical output timers (see the Programmable Output Section).
27 Parameter
Range/Curve
Increment
Undervoltage Pickup
10 to 200 VAC
1 volt
Time Delay
0 to 60 seconds
1 second
The 27 undervoltage elements are disabled in the factory default settings.
Table 1-13. 27 (U<) Characteristics