Ice Protocol Manual

Table of Contents Ice Protocol

1. Introduction and purpose
2. Risks
3. Safety measures
4. Detection of icing and actions
5. De-icing and commissioning inspection
6. Controlled de-icing and commissioning
7. Emergencies
8. Updating, management and release protocol
9. Sources and references consulted

Attachments

1. Introduction and purpose

This protocol was drawn up by NedZero (formerly NWEA) to ensure the safety of people and equipment during icing on wind turbines. This protocol applies to wind turbines with an ice detection system.

In the Netherlands, conditions occur on average two to seven days per year in which ice formation can occur on wind turbines. In most cases, the ice buildup itself does not cause the hazard, but the falling fragments of the deposited ice do. This is an unpredictable process due to nature-related circumstances.

The falling of ice and the size of the chunks is not predictable. Research has been conducted in various countries in the context of safety. It is not yet known from these studies that this leads to unacceptable risks for the environment. Due to its natural character, it is also not specific to wind turbines.

Important influences are the ambient temperature, the temperature of the wind turbine itself, the humidity, the wind force and the wind direction. All in all, a process that is difficult to control and difficult to predict, which requires the necessary attention and measures. To this end, the wind turbine operators have drawn up this Safety Protocol in joint consultation with instructions on how to deal with this.

This protocol describes the following:
• What are the risks for the immediate vicinity of the wind turbine?
• Where does the ice end up?
• How is icing determined?
• What is the action of the wind turbine during ice detection?
• How should park managers act when reporting ice build-up?
• What action should be taken on site at the wind turbine regarding safety?
• When can the wind turbine be put into operation?
• Who is responsible and who has authority?
• Which Safety Regulations are used?

The underlying Safety Protocol consists of an extensive description of possible circumstances and situations, their risks, measures and actions to be taken. Suggestions are also made for attachments to be added. These must be added by the user himself.

Since changes may occur with regard to the situations and circumstances surrounding wind turbines, such as industrial expansion or establishments by companies, parts of this protocol will have to be changed.

These parts will be included in the appendices to be attached and can be replaced without issuing a new protocol. The further content, or text, is fixed and therefore version-bound.
If changes need to be made, this will mean the issuance of a new version.
All attachments must be supplied specifically for each operator with company-specific instructions.

2. Risks

2.1 General

Ice deposits on, and in particular, the rotor blades of the wind turbine can create risks due to the loosening and falling of this ice. These fragments can injure passers-by and cause damage to buildings and other equipment in the immediate vicinity of the wind turbine.

Since it is not possible to predict exactly the size and speed at which the ice will fall, safety measures will have to be taken to minimize risks. The measures to be taken are shown later in the protocol.

2.2. Consequences of ice build-up on wind turbines

The basic principle is that falling ice poses a direct risk of injury to unprotected people, such as pedestrians and cyclists. There is an economic risk for buildings, vehicles and other equipment. There are two situations:

2.2.1 Fragments of ice from a rotating turbine
Flying ice fragments can pose a danger to the environment. This depends on the size, shape and mass of the fragment, the moment of dislodgement and the speed of the rotor. This is only acceptable if this is a manageable process during the so-called “Controlled turning of ice”, as described in Chapter 6 of this Safety Protocol.

To prevent pieces of ice from being thrown away, the wind turbine is immediately taken out of operation as soon as the ice detection system with which the wind farm is equipped gives a signal of possible ice formation. Decommissioning does not mean that the rotor (blades) of the wind turbine come to a complete standstill. The speed is then < 1 rpm, so no pieces of ice are thrown away.

2.2.2 Fragments of ice from a stationary turbine
a) In the so-called up-wind position (head into the wind)
When the turbine is stationary, it is in principle no different from any other structure, such as a tower, antenna mast, high-voltage pylons and overhead lines, with regard to ice formation and the risks of falling ice. However, the position of the rotor blades can vary and therefore determines the danger zone. The ice falls in the vicinity of the wind turbine. This is acceptable in places where there are no persons, buildings and/or other equipment, so that the effect of the falling ice is minimal and no additional measures need to be taken.
b) In the so-called fixed cross angle
The same situation as in a), but the nacelle/rotor has been rotated and fixed in the safest position on the tower, noting that fixing depends on the turbine.

At locations where people and equipment are regularly present or where there are buildings, the precautions described in the work instructions must be taken. The best measure is to clear the danger zone around the wind turbine by evacuating people and mobile equipment from the immediate vicinity of the wind turbine.
This measure must be followed or started as soon as ice has actually formed on the blades or nacelle of a turbine, and be ready before the thaw occurs.

2.3 Risk categorization per wind turbine location

Since there is a significant difference in the risk aspects at the different wind turbine locations, all locations have been categorized into a risk level. The locations differ on three levels:

Prime location
“Non-critical”, turbine locations in the open field, on non-through roads and on public closed grounds.

B location
“Limited-critical”, turbine locations near main roads, near manned buildings and on non-public closed grounds.

C location
“Critical”, turbine locations close to buildings and where there are pedestrians and cyclists. (This depends on the location of the entire situation around the turbine. This concerns the risk to the immediate environment that the turbine can cause if there is ice on it. So each turbine location must be assessed separately and described in an appendix. possibly with measures to be taken in the event of an emergency.)

All turbine locations must be provided with a category number per operator on the overview list of all wind turbines of the relevant operator. This protocol can serve as a guideline for all locations, depending on existing regulations. The Overview of Fixed Crossing Angle and Risk Category is attached as Appendix IV to this protocol.

Assessed categorization should be used as a priority list in the event of an emergency. This list can also be used for the controlled dispensing of ice in the correct order. The aforementioned list can be revised during the annual evaluation depending on developments in the area.

2.4 Risk Inventory & Evaluation (RI&E)

This principle means that an attempt is always made to remove the danger at the source first. If this has insufficient effect, local and individual measures will be taken successively.

Such measures may differ per wind turbine (operator), depending on the brand and type of wind turbine and the associated technical options. Each operator has described this in its own Risk Inventory and Evaluation Plan (RI&E) for the relevant project/location, an example of which is attached as Appendix VI.

3. Safety measures

3.1 Automatically decommissioning wind turbines upon ice detection

If the farm/wind turbine is equipped with an ice detection system, the wind turbines are immediately automatically taken out of service as soon as the ice detection system sends a signal of possible ice formation. Decommissioning does not mean that the rotor (blades) of the wind turbine come to a complete standstill. The speed is then < 1 rpm, which ensures that no pieces of ice are thrown away.

Commissioning will only take place after the relevant park manager has ensured that the danger of falling ice has passed. Each operator has described its own start-up procedure after ice detection. The Work Instruction procedure for Detecting and Reporting Ice Deposition has been added as Appendix I to this Safety Protocol.

3.2 Fixing the nacelle/rotor in the safest defined position, the fixed crown angle

It varies per location in which position the nacelle and therefore the rotor poses the least risk to the immediate environment. Therefore, the safest position of the nacelle and rotor must be determined per location by the operator, if applicable in consultation with the competent authority and any third parties with rights to land under the wind turbines.

This results in a desired fixed angle of icing defined per location, if applicable to the location in question and up to a certain wind speed that is turbine-specific. This is further determined in the relevant work instruction.

Normally when a wind turbine is in operation, the rotor blades are in a plane perpendicular to the wind direction.

The crossing angle per wind turbine is stated in the “Overview of fixed crossing angle and risk category”, which is attached in Appendix IV. The fixed head angle is also shown on each situational drawing for each wind turbine. The fixed angle of rotation is determined with respect to the north and the direction of rotation is clockwise.

The intersection angle and thus the sales area can be adjusted by the operator at the request of an involved party ^[1] , such as the land owner/land user. If a landowner/user wishes to deviate from these Safety Measures, this is his or her responsibility.

[1] For example, when a landowner has implemented a new site layout and it is therefore desirable to adjust the cross angle, temporarily or permanently. The operator is responsible for assessing possible new risks in such cases and reporting them to (its own management and) the competent authority.

3.3 Clearing and cordoning off

To ensure the safety of unprotected persons, it is important to exclude and remove unauthorized persons from the risk area. This is specified in the work instruction.

If practical experience shows that guaranteeing safety would benefit from changing the Safety Aspects, the wind turbine operators will implement this. The parties involved will also be informed about this.

Specific Safety Measures vary per operator, per location of a wind turbine, per brand and type of turbine and the category in which the turbine is classified. This depends on the conditions on location under and around the wind turbine.

Each operator has included work instructions for fixing in the fixed corner angle, clearing and cordoning off the risk area for its wind farm in the “Work Instructions for Detecting and Reporting Ice Deposition”, Appendix I of this Safety Protocol.

4. Detection of icing and actions

4.1 Observation

Determining potential ice formation takes place automatically. This happens in 2 ways:

4.1.1 By means of special ice sensors and/or monitoring systems installed on one or more wind turbines in the wind farm. The sensors detect ice build-up and/or monitor weather conditions. These systems must generate an error message when they do not function properly.

4.1.2 And/or by means of individual software detection. This recognizes a deviation in the Power Curve of the turbine and links possible ice formation to it.

As soon as icing is detected, a signal is sent to the wind farm server / the specific wind turbine. The wind turbines are then automatically switched off immediately.

The exact decommissioning procedure per operator is included in Appendix I.

4.2 Actions and work instructions

When an ice detection report is received, each operator uses its own specific Work Instructions. These depend on the turbine brand, type and the version of the ice detection system. For this purpose, reference is made to the company's own work instructions, such as the Work Instructions for Detecting and Reporting Ice Deposition separately in the attached Appendix I (company's own instructions).

The Work Instruction is also shown schematically in the “Flow Diagram Ice Detection Report” attached as Appendix II.

5. De-icing and commissioning inspection

5.1 Inspection

Before the wind turbine can be put back into operation, it must be free of ice again. This must be ensured, for example by visual inspection or by using ice detection aids such as leaf monitoring equipment. If a visual inspection on location is chosen, it may be necessary for the manager to enter the risk area for this purpose, but this is only allowed taking into account personal safety and protective equipment in accordance with the Safety Regulations, see Appendix VI. If visual inspection is not or insufficiently possible due to, for example, poor visibility, fog, twilight or darkness and there is no other way to ensure that the wind turbine is free of ice, the wind turbine must not be started. Until then, the measures previously taken will be maintained.

5.2 Commissioning

The manager will commission the wind turbine in accordance with its own specific Work Instructions for Detecting and Reporting Ice Deposition. These Work Instructions are shown in the attached Appendix I.

The Work Instructions are also shown schematically in the “Flow Diagram Ice Detection Report” which is attached as Appendix II.

6. Controlled calibration and commissioning

6.1 General and safety

To limit the duration and risks of falling ice, it can be decided per location, if applicable with the permission of the competent authority, to spin the deposited ice off the blades in a controlled manner.

In general, controlled turning is used for so-called frost ice build-up on the blades. This rime ice is formed when there is little wind, the air temperature is close to freezing point and at the same time there is very high humidity, due to fog or low clouds.

Very small water droplets then crystallize and settle on the blades, because they are colder (below freezing point) than the outside air due to the rotation. Crystallization is enhanced by the so-called Bernoulli effect, in which pressure and temperature differences arise on and along the rotor blade. This process continues and a layer of very fluffy white ice grows, resembling frozen snow.

Because the frost ice consists of crystals with a lot of air between them, it is very lightweight. This means that it poses little danger when landing. When it thaws, the ice will become more compact and glassy. This will also increase the mass and create greater risks.

On the other hand, turning off the so-called frost ice is only possible when a thaw has occurred. Freezing ice is very compact in structure and has a greater density than rime ice. This makes the effect greater when falling. Moreover, it is not technically responsible to operate the wind turbine with a layer of heavy icy ice on it. Thawing frost ice can be turned off in a controlled manner.

Particularly at locations where the danger of falling ice and the associated closed-off safety zone has caused a lot of nuisance, controlled turning of the ice offers advantages.

This advantage lies in the fact that at that moment it is known in advance that the ice will come off and you do not have to wait until it has fallen. Falling through the thaw is a completely uncontrolled process. Spinning off, taking into account sufficient additional safety measures, is a controlled process.

The Risk categorization of all turbine locations is shown in the “Overview of fixed intersection angle and risk category”, which is attached as Appendix IV.

6.2 Implementation and measures

Further implementation and measures are in accordance with the agreements made with the competent authority and are described in the manager's work instructions (Appendix I).

Before starting up, the manager follows the normal Work Instructions for Detecting and Reporting Ice Deposition for commissioning after reporting ice detection. These Work Instructions are shown separately in the attached Appendix I.

This chapter is also shown schematically in the “Flow Diagram Ice Detection Report” in Appendix II.

7. Emergencies

In the event of emergencies at the wind turbines due to ice build-up or any consequences thereof, the manager(s) or the fault number of the operator in question can be contacted. The contact persons are on the list “Operator contact persons in the event of emergencies”, which is attached as Appendix V to this protocol.

The address for submitting written requests is also stated on the aforementioned “Third Party Contact Notification List”.

8. Updating, management and release protocol

Since new developments and activities may occur in the vicinity of the wind turbines, the wind turbine operators will annually review (the appendices to) this Safety Protocol and update it if necessary.

Updating means that an annual check per wind turbine location takes place before the winter months. It is recorded and assessed whether any changes/expansion have taken place under and around the wind turbines in question in the past year, which influence the content of this protocol.

The marked corners of the danger zones to be cordoned off will also be checked for condition and presence. And maintain or replace if necessary. Furthermore, a check will be carried out on the “Third Party Contact Notification List”, checking whether the persons included, telephone numbers and e-mail addresses are still up to date.

If any changes/expansions are found, these will be mapped out and the appendices will be adjusted where necessary. If this concerns significant adjustments, including different positioning of the crossing angle or area/roads to be cordoned off, consultation will first take place with the competent authority and site manager/owner/user.

The agreements made will be incorporated in the appendices by replacing the existing Situation Drawing. If major procedural or textual adjustments need to be made to the protocol for this purpose, this will result in a new version of the protocol.

If necessary, a new version of the protocol or individual adjustments to the Annex(es) will be issued annually to existing copy holders with an explanation of the changes. Any new parties involved will also receive a copy, with a more detailed explanation of the content and operation of the protocol.

Each operator will maintain its own “Safety Protocol Issuance List”, see Appendix VII, with the names of copy holders to whom a copy has been issued. This makes it known who the copy holders are, and the issuance of a new and/or amended version can also be checked.

The recipient of a copy must initial the list before receiving it. In addition, the recipient is responsible for further issuing and managing copies within his/her own organization.

9. Sources and references consulted

9.1 General

Various sources have been consulted to assist in drawing up the safety protocol and to test practical experiences. These sources include existing literature, research conducted as well as telephone and personal contacts with experienced experts.

Relevant data from the sources mentioned have been applied, processed or referred to in this safety protocol.

9.2 Sources

Wind Turbine Risk Zoning Manual, version 2, January 2005, H. Braam, ECN

Risk analysis Wind turbine near the Staart van Houten, H. Braam, ECN, September 2002; Deutsches Windenergie Institut GmbH – DEWI

Risk Analysis of ice throw from wind turbines, Henry Seifert, 2003

http://www.dewi.de/dewi/fileadmin/pdf/publications/Studies/Icing/stpoelten.pdf

Wind energy in cold climate

Finish Meteorological Institute FMI

Risk analysis of controlled ice removal, TNO report, August 2010, J. Reinders and Ingrid Heidebrink

9.3 Endnotes

1) Telephone conversation with Henk Braam, ECN

2) The labor hygiene strategy principle consists of:
a. Source measures: prevent hazards or remove the cause of the problem;
b. Collective measures if source measures are not possible;
c. Individual measures: if collective measures are not possible or do not (yet) provide a sufficient solution, local measures are taken.

As a final option, Personal Protective Equipment (PBs) can be provided.

Attachments (see PDF top of page)

I. Work instructions for detecting and reporting ice formation
II. Flow Diagram Ice Detection Message
III. Notification list Third party contacts
IV. Overview list of Fixed Crossing Corner and Risk Category
V. Contact persons in case of emergencies
VI. Safety regulations
VII. Safety Protocol Issue List
VIII. Situation drawings of wind turbines for Ice Detection Notification