Table of Contents
Advertisement
GEK-106261
GEK-106261 2 PRODUCT DESCRIPTION
The DIAC is a self-powered, single-phase, digital overcurrent relay. This digital overcurrent relay is sometimes
referred to as the 'Type 66K relay', as it was designed to replace the IAC66K Motor Protection relay. The Type
66K relays are single-phase, current operated AC devices designed for motor protection. They utilize 16
selectable time-current characteristics (shown on pages 2–3 to 2–18).
Each relay consists of a time overcurrent unit, a dual-rated target seal-in unit, and a hinge-type instantaneous
overcurrent unit. The available ranges in amperes of these units, as well as information on their continuous rat-
ing, contact rating, and top ratings are given in Section 2.3: RATINGS.
The DIAC 66K is packaged in a GE S1 style case. See Figure 5–4: DIAC PANEL MOUNTING AND DRILLING
on page 5–5 section for mounting dimensions. The internal connections are shown in Figure 5–1: DIAC TYPE
66K INTERNAL/EXTERNAL CONNECTIONS on page 5–2. The DIAC 66K uses waveform sampling of the
current input together with appropriate algorithms to provide time overcurrent (TOC) and instantaneous over-
current (IOC) functions.
The DIAC Type 66K is especially suited for motor protection. The relay contains an electronic (IOC) high drop-
out instantaneous unit to discriminate between motor-running overload and locked-rotor current. This is
accomplished by setting pickup of the high dropout unit (50/B) between motor full-load current and locked-rotor
current as illustrated in Figure 5–5: MOTOR PROTECTION CHARACTERISTIC CURVE on page 5–6, with the
normal (EM) dropout instantaneous unit (50/A) set above locked-rotor current. The TOC reset characteristics
can emulate those of an induction disk or set for fast reset with no intentional delay. The time overcurrent unit
must coordinate with the motor thermal limit. Typical settings to accomplish this are listed in the table below:
Table 2–1: DIAC 66K SETTING RANGE
UNIT / FUNCTION
Time Overcurrent Unit
Normal Dropout Instantaneous Overcurrent Unit
High Dropout Instantaneous Overcurrent Unit
The user must determine the specific settings which will provide the required protection for his machine, and
select a relay model having the operating ranges needed to obtain these settings.
With settings as illustrated in Figure 5–5: MOTOR PROTECTION CHARACTERISTIC CURVE on page 5–6
and external connections shown in Figure 5–3: TYPICAL EXTERNAL CONNNECTIONS FOR MOTOR PRO-
TECTION on page 5–4, the operation of the DIAC66K relay will be as follows:
•
For motor overloads, the time overcurrent unit (51) will time out, picking up an external auxiliary 51X, which
sounds an alarm (Stud # 2).
•
For the locked-rotor condition, the high-dropout unit (50/B) will pick up instantaneously and the TOC (51)
will pick up with a time delay consistent with the motor thermal limit. When both units have operated, the
breaker will be tripped (Stud 10).
•
For a fault, the (EM) normal dropout instantaneous unit (50/A) will pick up instantaneously and trip the
breaker (Stud 3).
NOTE: The relay can also be used by setting the Instantaneous HDO setting switch to the lowest set-
ting, not including 0. This will allow the Instantaneous HDO unit to pickup at 0.1 A or 0.5 A, thus
enabling TOC to operate independently using stud 10. Use stud 3 as the Standard High Set IOC.
GE Power Management
51
50/A
50/B
DIAC Type 66K Digital Overcurrent Relay
2 PRODUCT DESCRIPTION
PICKUP SETTING (multiples
of nominal current 1A/5A)
1.5 to 40
8 to 15
1.1 to 10
2.1 GENERAL
2
2.2 APPLICATION
2-
1
Advertisement
Table of Contents
