DD-11 type grounding relayDetailed product description：

1 Purpose
The DD-11 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.

Overview of Structure 2
A relay is an instantaneous action composed of electromagnetic principles. The electromagnetic system has two coils, and when current passes through them, a magnetic flux that forms electromagnetic torque is generated in the magnetic conductor.
Due to the requirement of high sensitivity for relays used as grounding protection in small grounding systems, compensation windings are added to both coils in addition to using hairspring with small reaction torque. After they are connected in series, they form a closed circuit through a capacitor (C=0.5uf) to compensate for the reactance of the magnetizing coil, reducing the power required to generate the same magnetic flux in the magnetic conductor, improving the sensitivity of the relay, and reducing losses.
The outlet of the 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.
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.
Relays are installed on vertical panels and can be wired in front of or behind the board.
The internal wiring of the relay is shown in Figure 1:

Figure 1

Technical data of DD-11 grounding relay
3.1 The setting range of relay operating current and coil impedance values are shown in the following table:

model	Setting range (mA)	Coil series connection		Parallel connection of coils
		Action current mA	Impedance (Ω)	Action current mA	Impedance (Ω)
DD-11/40	10-40	10-20	eighty	20-40	twenty
DD-11/50	12.5-50	12.5-25	fifty-two	25-50	thirteen
DD-11/60	15-60	15-30	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, rated rate 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 near 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 non charged metal can withstand AC 50Hz, voltage 2kV, and undergo a 1-minute test without breakdown or flashover.
3.11 The weight of the relay shall not exceed 1.5k8.
The appearance and opening size of DD-11 relay are shown in Figure 2 and Figure 3.


Figure 2 Outline dimension diagram

Figure 3 Hole Size Diagram

4 Ordering Instructions
When placing an order, please specify:
4.1 Name and model of relay.
4.2 Maximum setting current (mA).
4.3 Wiring method (front board wiring or back board wiring); If not specified, supply according to the wiring at the back.

DD-11 type grounding relay（No image available）