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Low-Frequency Low-Voltage Load Shedding
Low-Frequency Low-Voltage Load Shedding Device | UFUVLS Relay for Power Grid Stability
  1. Low-Frequency Low-Voltage Load Shedding
  2. Low-Frequency Low-Voltage Load Shedding Device | UFUVLS Relay for Power Grid Stability

Low-Frequency Low-Voltage Load Shedding Device | UFUVLS Relay for Power Grid Stability

ATN-8694 Microprocessor-based Low-Frequency Low-Voltage Load Shedding Device stabilizes power systems against frequency and voltage drops from power shortage. It performs staged automatic load shedding to restore supply-demand balance.

Communication Mode:Optional: RS-485, CAN bus, Ethernet, IEC 60870-5-103 , IEC 61850

In-house Factory & Technical Team, OEM ODM Custom Electrical Equipment

Description

Overview of Low-Frequency Low-Voltage Load Shedding Device

  • ATN-8694 Microprocessor-based Low-Frequency Low-Voltage Load Shedding Device stabilizes power systems against frequency and voltage drops from power shortage. It performs staged automatic load shedding to restore supply-demand balance.
  • This Power System Emergency Load Shedding Device measures dual-section busbar voltage, equipped with 5 standard and 3 special shedding cycles for underfrequency and undervoltage conditions. Flexible configurable output supports shedding up to 60 load branches, stabilizing grid frequency & voltage and securing reliable power supply.

Technical Features

  • Underfrequency load shedding: When active power shortage causes system frequency drop, the device automatically sheds partial loads based on frequency deviation to restore power balance. Equipped with 5 basic stages and 3 special stages.
  • Undervoltage load shedding: When reactive power shortage triggers voltage drop, partial loads will be cut off automatically to rebalance power supply and load, with 5 basic and 3 special stages available.
  • df/dt and du/dt blocking functions prevent mal-operation induced by short circuit, load rebound and abnormal frequency & voltage fluctuation.
  • Busbar split running switch enables setting of split or parallel operation mode for double busbars.
  • Modular program design ensures flexible configuration and easy function modification.
  • Reliable PT broken line detection avoids false operation of undervoltage protection.
  • Max. 21 user-definable binary input channels.
  • Programmable output: Trip matrix setting allows flexible relay output selection. Contacts support auto-reset trip type and manual-reset signal type.
  • Supports network timing and IRIG-B timing via RS485 port.
  • Dual 100M Ethernet ports and one RS485 port, compatible with IEC60870-5-103, 104 and Modbus protocols.
  • Stores 16 fault records, sampling up to 13 analog channels at 1ms interval in standard Comtrade format.
  • Advanced color touch LCD panel features prolonged service life.

Basic Feature Configuration of Frequency Voltage Emergency Control Relay

  • Underfrequency load shedding: Cuts partial loads against frequency drop caused by active power shortage to restore power balance. Configured with 5 basic stages, 3 special stages, 2 accelerated shedding stages and 2&3 combined accelerated shedding stages.
  • Accelerated underfrequency shedding: Sheds loads rapidly based on df/dt value when frequency declines sharply. Accelerates stage 2 or stage 2&3 shedding along with stage 1 action to halt frequency collapse.
  • Undervoltage load shedding: Removes partial loads to recover normal voltage level under reactive power deficit. Equipped with 5 basic stages, 3 special stages and corresponding accelerated shedding functions.
  • Accelerated undervoltage shedding: Fast load shedding by dU/dt criterion curbs rapid voltage drop, prevents voltage collapse and restores voltage within permissible range.
  • df/dt and du/dt slip blocking function
  • PT broken line blocking and alarm function
  • Undervoltage blocking function
  • Busbar split operation switch supports split or parallel operation mode
  • IRIG-B and SNTP time synchronization

Low-Frequency Low-Voltage Load Shedding

IEC 60255-118-1 Load Shedding Relay Setting Parameters Table

No. Setting Name Range Unit Remark
1 1st Stage Underfrequency Setting of Bus I 45～50 Hz
2 2nd Stage Underfrequency Setting of Bus I 45～50 Hz
3 3rd Stage Underfrequency Setting of Bus I 45～50 Hz
4 4th Stage Underfrequency Setting of Bus I 45～50 Hz
5 5th Stage Underfrequency Setting of Bus I 45～50 Hz
6 1st Special Underfrequency Setting of Bus I 45～50 Hz
7 2nd Special Underfrequency Setting of Bus I 45～50 Hz
8 3rd Special Underfrequency Setting of Bus I 45～50 Hz
9 df/dt Setting for 2-stage Accelerated Shedding of Bus I 0.20～20 Hz/s
10 df/dt Setting for 2-3 Stage Accelerated Shedding of Bus I 0.20～20 Hz/s
11 Frequency Variation Rate Block Setting of Bus I 0.20～20 Hz/s
12 1st Stage Underfrequency Time Delay of Bus I 0.05～10 s
13 2nd Stage Underfrequency Time Delay of Bus I 0.05～10 s
14 3rd Stage Underfrequency Time Delay of Bus I 0.05～10 s
15 4th Stage Underfrequency Time Delay of Bus I 0.05～10 s
16 5th Stage Underfrequency Time Delay of Bus I 0.05～10 s
17 1st Special Underfrequency Time Delay of Bus I 0.05～10 s
18 2nd Special Underfrequency Time Delay of Bus I 0.05～10 s
19 3rd Special Underfrequency Time Delay of Bus I 0.05～10 s
20 2-stage Accelerated Underfrequency Delay of Bus I 0.05～10 s
21 2-3 Stage Accelerated Underfrequency Delay of Bus I 0.05～10 s
22 1st Stage Undervoltage Setting of Bus I 45～50 V
23 2nd Stage Undervoltage Setting of Bus I 45～50 V
24 3rd Stage Undervoltage Setting of Bus I 45～50 V
25 4th Stage Undervoltage Setting of Bus I 45～50 V
26 5th Stage Undervoltage Setting of Bus I 45～50 V
27 1st Special Undervoltage Setting of Bus I 45～50 V
28 2nd Special Undervoltage Setting of Bus I 45～50 V
29 3rd Special Undervoltage Setting of Bus I 45～50 V
30 dU/dt Setting for 2-stage Accelerated Shedding of Bus I 0.20～20 V/s
31 dU/dt Setting for 2-3 Stage Accelerated Shedding of Bus I 0.20～20 V/s
32 Voltage Variation Rate Block Setting of Bus I 0.20～20 V/s
33 1st Stage Undervoltage Time Delay of Bus I 0.05～10 s
34 2nd Stage Undervoltage Time Delay of Bus I 0.05～10 s
35 3rd Stage Undervoltage Time Delay of Bus I 0.05～10 s
36 4th Stage Undervoltage Time Delay of Bus I 0.05～10 s
37 5th Stage Undervoltage Time Delay of Bus I 0.05～10 s
38 1st Special Undervoltage Time Delay of Bus I 0.05～10 s
39 2nd Special Undervoltage Time Delay of Bus I 0.05～10 s
40 3rd Special Undervoltage Time Delay of Bus I 0.05～10 s
41 2-stage Accelerated Undervoltage Delay of Bus I 0.05～10 s
42 2-3 Stage Accelerated Undervoltage Delay of Bus I 0.05～10 s
43 1st Stage Underfrequency Setting of Bus II 45～50 Hz
44 2nd Stage Underfrequency Setting of Bus II 45～50 Hz
45 3rd Stage Underfrequency Setting of Bus II 45～50 Hz
46 4th Stage Underfrequency Setting of Bus II 45～50 Hz
47 5th Stage Underfrequency Setting of Bus II 45～50 Hz
48 1st Special Underfrequency Setting of Bus II 45～50 Hz
49 2nd Special Underfrequency Setting of Bus II 45～50 Hz
50 3rd Special Underfrequency Setting of Bus II 45～50 Hz
51 df/dt Setting for 2-stage Accelerated Shedding of Bus II 0.20～20 Hz/s
52 df/dt Setting for 2-3 Stage Accelerated Shedding of Bus II 0.20～20 Hz/s
53 Frequency Variation Rate Block Setting of Bus II 0.20～20 Hz/s
54 1st Stage Underfrequency Time Delay of Bus II 0.05～10 s
55 2nd Stage Underfrequency Time Delay of Bus II 0.05～10 s
56 3rd Stage Underfrequency Time Delay of Bus II 0.05～10 s
57 4th Stage Underfrequency Time Delay of Bus II 0.05～10 s
58 5th Stage Underfrequency Time Delay of Bus II 0.05～10 s
59 1st Special Underfrequency Time Delay of Bus II 0.05～10 s
60 2nd Special Underfrequency Time Delay of Bus II 0.05～10 s
61 3rd Special Underfrequency Time Delay of Bus II 0.05～10 s
62 2-stage Accelerated Underfrequency Delay of Bus II 0.05～10 s
63 2-3 Stage Accelerated Underfrequency Delay of Bus II 0.05～10 s
64 1st Stage Undervoltage Setting of Bus II 45～50 V
65 2nd Stage Undervoltage Setting of Bus II 45～50 V
66 3rd Stage Undervoltage Setting of Bus II 45～50 V
67 4th Stage Undervoltage Setting of Bus II 45～50 V
68 5th Stage Undervoltage Setting of Bus II 45～50 V
69 1st Special Undervoltage Setting of Bus II 45～50 V
70 2nd Special Undervoltage Setting of Bus II 45～50 V
71 3rd Special Undervoltage Setting of Bus II 45～50 V
72 dU/dt Setting for 2-stage Accelerated Shedding of Bus II 0.20～20 V/s
73 dU/dt Setting for 2-3 Stage Accelerated Shedding of Bus II 0.20～20 V/s
74 Voltage Variation Rate Block Setting of Bus II 0.20～20 V/s
75 1st Stage Undervoltage Time Delay of Bus II 0.05～10 s
76 2nd Stage Undervoltage Time Delay of Bus II 0.05～10 s
77 3rd Stage Undervoltage Time Delay of Bus II 0.05～10 s
78 4th Stage Undervoltage Time Delay of Bus II 0.05～10 s
79 5th Stage Undervoltage Time Delay of Bus II 0.05～10 s
80 1st Special Undervoltage Time Delay of Bus II 0.05～10 s
81 2nd Special Undervoltage Time Delay of Bus II 0.05～10 s
82 3rd Special Undervoltage Time Delay of Bus II 0.05～10 s
83 2-stage Accelerated Undervoltage Delay of Bus II 0.05～10 s
84 2-3 Stage Accelerated Undervoltage Delay of Bus II 0.05～10 s

 

FAQ

Q：In which projects are UFLS and UVLS relays applied?

A:

Isolated grid systems: including captive power plants, microgrids and island power grids. It rapidly balances local power after disconnection from main grid to prevent blackout.

Weak tie-line systems: remote rural, forest power networks and grid terminals with dense industrial loads, featuring low tie-line capacity and vulnerability to instability.

Critical power supply projects: metallurgy, chemical and other continuous production industries. Load shedding retains core facilities to avoid equipment damage and economic losses.

New energy grid-connected projects: regional grids with high wind and solar penetration, mitigating power imbalance caused by renewable energy output fluctuation.

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