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Questions and Answers
What defines surge voltage?
What defines surge voltage?
What device is used to protect against surge voltage?
What device is used to protect against surge voltage?
Which scenario can cause surge voltage?
Which scenario can cause surge voltage?
What is the situation described as overvoltage?
What is the situation described as overvoltage?
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Which cause leads to overvoltage due to a faulty situation?
Which cause leads to overvoltage due to a faulty situation?
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Which type of relay is used to protect against overvoltage situations?
Which type of relay is used to protect against overvoltage situations?
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What is a common result of load variation in an electrical system?
What is a common result of load variation in an electrical system?
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Which of the following is NOT a typical cause of surge voltage?
Which of the following is NOT a typical cause of surge voltage?
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What is required for new electrical installations after April 2010 according to local regulations?
What is required for new electrical installations after April 2010 according to local regulations?
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Which statement about the over and under voltage relay is true?
Which statement about the over and under voltage relay is true?
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What does the internal relay of the over and under voltage relay control?
What does the internal relay of the over and under voltage relay control?
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Where should an over voltage protective device be installed?
Where should an over voltage protective device be installed?
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How does the Surge Protection Device (SPD) function in an electrical installation?
How does the Surge Protection Device (SPD) function in an electrical installation?
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What is the primary role of an over and under voltage relay?
What is the primary role of an over and under voltage relay?
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What advantage does the newer technology of combined O/U relays with a power relay offer?
What advantage does the newer technology of combined O/U relays with a power relay offer?
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In what scenario is it recommended to use over and under voltage relay protection?
In what scenario is it recommended to use over and under voltage relay protection?
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What is the primary purpose of a Type 1 SPD?
What is the primary purpose of a Type 1 SPD?
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What is the recommended maximum total lead length for connecting conductors to SPDs?
What is the recommended maximum total lead length for connecting conductors to SPDs?
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Which SPD type is the main protection system for low voltage electrical installations?
Which SPD type is the main protection system for low voltage electrical installations?
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Where should Type 3 SPDs be installed?
Where should Type 3 SPDs be installed?
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What characteristic of SPDs changes when a transient overvoltage occurs?
What characteristic of SPDs changes when a transient overvoltage occurs?
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What is recommended when using more than one type of SPD?
What is recommended when using more than one type of SPD?
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What is a crucial aspect of the installation of SPDs to minimize inductive voltage drops?
What is a crucial aspect of the installation of SPDs to minimize inductive voltage drops?
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What role does the surge current play in relation to SPD during high impedance?
What role does the surge current play in relation to SPD during high impedance?
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Study Notes
Overvoltage Protection
- Two main types of overvoltage: surge voltage and excess voltage
- Surge voltage: A short burst of high voltage lasting microseconds. Lightning and heavy current events are common causes. Surge Protection Devices (SPDs) mitigate this type.
- Typical causes of surge voltage: Lightning, heavy current switching, heavy current faults
- Excess voltage: A sustained voltage exceeding the nominal voltage (typically +/-10%). Causes include: a higher voltage generated in the supply system (e.g., photovoltaic cells), a combination of load variations and substation transformer voltage regulation settings, and a faulty neutral conductor. Over/under voltage relays are used to protect against this type.
Surge Protection Devices (SPD)
- SPD function: Designed to protect against surge voltage
- SPD connection: Parallel to the power supply, on all levels of the network
Over/Under Voltage Relay
- Function: Protects against voltage variations exceeding normal limits (+/-10%). Primarily a voltage sensor that triggers a larger relay when voltage exceeds pre-set limits
- Operation: Detects voltage too high or too low
- Current handling capacity: The internal relay handles small currents, triggering a larger relay to handle the installation's higher currents. SPDs are specifically designed to handle surge currents and protect other equipment from them.
- Modern relay units: Some units combine over/under voltage and power relays in a single unit for easier installation.
Legal Requirements
- Electrical installations (after April 2010): Need overvoltage protection
- Regulation compliance: Follow S.L.545.24 (LN225 of 2010)
- SPD Installation: Install SPD, immediately after the main switch/fuse or circuit breaker, as per the regulation
- Critical length of connecting conductors: Keep conductors to SPDs as short as possible to minimise voltage drop. Maximum length: 0.5m preferably, but not exceeding 1m. Refer to the manufacturer's recommendations
Types of SPDs
- Type 1 SPD: Primarily for service sector, industrial buildings, where lightning strikes might damage equipment
- Type 2 SPD: Main protection for low voltage electrical installations. Prevents over-voltages across switchboards
- Type 3 SPD: Low discharge capacity, supplement to Type 2 SPDs. Generally close to sensitive equipment to handle additional surges.
SPD Connection
- Connection method: Always connect across phase and neutral conductors (or three phases) in a 3-phase system
- Wiring location: Typically between the main switch/circuit breaker and RCD.
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Description
Test your knowledge on overvoltage protection, focusing on the differences between surge voltage and excess voltage. Learn about Surge Protection Devices (SPDs) and the role of over/under voltage relays in safeguarding electrical systems. Gain insights into typical causes and functions of these protective measures.
