DD-11Q type grounding relayDetailed product description：

1 Purpose
1.1 DD-1lQ type grounding relay is an instantaneous overcurrent relay used for zero sequence overcurrent protection of three-phase AC generators and motors in small grounding current power systems.
When the zero point of the protected motor is grounded through impedance, the relay is connected to the differential circuit of the inverter.
When the relay is connected to a zero sequence current filter composed of three phase current transformers, a blocking relay should also be connected to prevent possible misoperation caused by unstable currents due to external transient short circuits.


Structure and Principle of DD-11Q Grounding Relay
2.1 The relay adopts embedded installation, and the main body is a plug-in structure.
2.2 The main body of this relay is the same as the DD-11 grounding relay.
2.3 Relays are constructed based on electromagnetic principles. The instantaneous action and electromagnetic system have two coils, and when current passes through them, a magnetic flux that forms electromagnetic torque is generated in the magnetic conductor.
2.4 As relays are used for grounding protection in small grounding systems, high sensitivity is required. Therefore, in addition to using a spring with a small reaction torque, compensation windings are added to both coils. After they are connected in series, they form a closed circuit through a capacitor (C=0.5 μ f) to compensate for the reactance of the magnetizing coil, reduce the power required to generate the same magnetic flux in the magnetic conductor, improve relay sensitivity, and reduce losses.
The output head of the 2.5 coil is connected to the terminal of the relay base, and a connecting piece is installed to allow the coil to be changed from series to parallel, thus doubling the setting value of the relay.
2.6 The adjustment of the set current is carried out by rotating the pointer on the dial to change the reaction torque of the balance spring, and the relay has a dynamic contact.
The internal wiring diagram of the 2.7 relay is shown in Figure 1.
The appearance and installation dimensions of the 2.8 relay are shown in Figure 2.  



Figure 1


Figure 2 Appearance and installation dimensions of DD11Q grounding relay

3 Technical data
The setting range of relay operating current and coil impedance value are shown in the table below.

model	Setting range (mA)	Coil series connection		Parallel connection of coils
		Action current (mA)	Impedance (Ω)	Action current (mA)	Impedance (Ω)
DD—11Q／40	10~40	10~20	eighty	20~40	twenty
DD—11Q／50	12．5～50	12．5～50	fifty-two	25~50	thirteen
DD—1lQ／60	15~60	15~60	thirty-six	30~60	nine

3.2 When relays of various specifications are connected in series or parallel with the coil, their impedance angle is+35 °.
3.3 Rated current 100mA, frequency 50Hz.
The accuracy of the scale on any set point shall not exceed ± 6%.
Scale accuracy=(maximum (or minimum) action value among five actions - scale value)/scale value X100%
The variation in motion during five measurements at the same set point shall not exceed 6%.
Action value deterioration=(maximum action value - minimum action value)/average of five actions X 100%
3.6 The return coefficient shall not be less than 0.5.
At the minimum setting current, the power consumption of the relay shall not exceed 0.012VA.
3.8 When the setting current is 1.2 times, the action time shall not exceed 0.3s; when the setting current is 3 times, the action time shall not exceed 0.1s.
When the voltage does not exceed 250V and the current does not exceed 0.5A, the breaking capacity of the relay contacts is 20W in a DC inductive load circuit (time constant of 5 × 10-3S) and 100VA in an AC circuit.
3.10 The dielectric strength between each circuit of the relay and the metal shell can withstand an AC of 50Hz and a voltage of 2kV for 1 minute without breakdown or flashover.
3.11 The weight of the relay shall not exceed 2kg.

4 Ordering Instructions
4.1 Relay name and model.
4.2 Maximum setting current of relay (mA).
4.3 Number of relays.

DD-11Q type grounding relay（No image available）